diff --git a/hail/hail/src/is/hail/types/physical/PArray.scala b/hail/hail/src/is/hail/types/physical/PArray.scala
index 8ec966eb8c1..a5ed89bbdce 100644
--- a/hail/hail/src/is/hail/types/physical/PArray.scala
+++ b/hail/hail/src/is/hail/types/physical/PArray.scala
@@ -1,8 +1,5 @@
 package is.hail.types.physical
 
-import is.hail.annotations.Annotation
-import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.types.virtual.TArray
 
 trait PArrayIterator {
@@ -17,7 +14,4 @@ abstract class PArray extends PArrayBackedContainer {
   final protected[physical] val elementRequired = elementType.required
 
   def elementIterator(aoff: Long, length: Int): PArrayIterator
-
-  override def genNonmissingValue(sm: HailStateManager): Gen[IndexedSeq[Annotation]] =
-    Gen.buildableOf[Array](elementType.genValue(sm)).map(x => x: IndexedSeq[Annotation])
 }
diff --git a/hail/hail/src/is/hail/types/physical/PBaseStruct.scala b/hail/hail/src/is/hail/types/physical/PBaseStruct.scala
index 2a6c1e7ca23..fddf0b248f4 100644
--- a/hail/hail/src/is/hail/types/physical/PBaseStruct.scala
+++ b/hail/hail/src/is/hail/types/physical/PBaseStruct.scala
@@ -1,9 +1,8 @@
 package is.hail.types.physical
 
 import is.hail.annotations._
-import is.hail.asm4s.{Code, _}
+import is.hail.asm4s._
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.expr.ir.EmitCodeBuilder
 import is.hail.types.physical.stypes.interfaces.SBaseStructValue
 import is.hail.utils._
@@ -144,10 +143,4 @@ abstract class PBaseStruct extends PType {
   override def loadCheapSCode(cb: EmitCodeBuilder, addr: Code[Long]): SBaseStructValue
 
   override lazy val containsPointers: Boolean = types.exists(_.containsPointers)
-
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    if (types.isEmpty) {
-      Gen.const(Annotation.empty)
-    } else
-      Gen.uniformSequence(types.map(t => t.genValue(sm))).map(a => Annotation(a: _*))
 }
diff --git a/hail/hail/src/is/hail/types/physical/PDict.scala b/hail/hail/src/is/hail/types/physical/PDict.scala
index 246e924bf68..c6cc0996ffd 100644
--- a/hail/hail/src/is/hail/types/physical/PDict.scala
+++ b/hail/hail/src/is/hail/types/physical/PDict.scala
@@ -1,8 +1,5 @@
 package is.hail.types.physical
 
-import is.hail.annotations._
-import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.types.physical.stypes.interfaces.SContainer
 import is.hail.types.virtual.TDict
 
@@ -15,7 +12,4 @@ abstract class PDict extends PContainer {
   def sType: SContainer
 
   def elementType: PStruct
-
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    Gen.buildableOf2[Map](Gen.zip(keyType.genValue(sm), valueType.genValue(sm)))
 }
diff --git a/hail/hail/src/is/hail/types/physical/PSet.scala b/hail/hail/src/is/hail/types/physical/PSet.scala
index 810bae84829..e6109bc58f8 100644
--- a/hail/hail/src/is/hail/types/physical/PSet.scala
+++ b/hail/hail/src/is/hail/types/physical/PSet.scala
@@ -1,13 +1,7 @@
 package is.hail.types.physical
 
-import is.hail.annotations._
-import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.types.virtual.TSet
 
 abstract class PSet extends PContainer {
   lazy val virtualType: TSet = TSet(elementType.virtualType)
-
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    Gen.buildableOf[Set](elementType.genValue(sm))
 }
diff --git a/hail/hail/src/is/hail/types/physical/PType.scala b/hail/hail/src/is/hail/types/physical/PType.scala
index 533766fad94..73bb1ba1fd2 100644
--- a/hail/hail/src/is/hail/types/physical/PType.scala
+++ b/hail/hail/src/is/hail/types/physical/PType.scala
@@ -3,14 +3,12 @@ package is.hail.types.physical
 import is.hail.annotations._
 import is.hail.asm4s._
 import is.hail.backend.{ExecuteContext, HailStateManager}
-import is.hail.check.{Arbitrary, Gen}
 import is.hail.expr.ir._
 import is.hail.types.{tcoerce, Requiredness}
 import is.hail.types.physical.stypes.{SType, SValue}
 import is.hail.types.physical.stypes.concrete.SRNGState
 import is.hail.types.virtual._
 import is.hail.utils._
-import is.hail.variant.ReferenceGenome
 
 import org.apache.spark.sql.Row
 import org.json4s.CustomSerializer
@@ -31,108 +29,6 @@ class PStructSerializer extends CustomSerializer[PStruct](format =>
     )
 
 object PType {
-  def genScalar(required: Boolean): Gen[PType] =
-    Gen.oneOf(
-      PBoolean(required),
-      PInt32(required),
-      PInt64(required),
-      PFloat32(required),
-      PFloat64(required),
-      PCanonicalString(required),
-      PCanonicalCall(required),
-    )
-
-  val genOptionalScalar: Gen[PType] = genScalar(false)
-
-  val genRequiredScalar: Gen[PType] = genScalar(true)
-
-  def genComplexType(required: Boolean): Gen[PType] = {
-    val rgDependents = ReferenceGenome.hailReferences.toArray.map(PCanonicalLocus(_, required))
-    val others = Array(PCanonicalCall(required))
-    Gen.oneOfSeq(rgDependents ++ others)
-  }
-
-  def genFields(required: Boolean, genFieldType: Gen[PType]): Gen[Array[PField]] = {
-    Gen.buildableOf[Array](
-      Gen.zip(Gen.identifier, genFieldType)
-    )
-      .filter(fields => fields.map(_._1).areDistinct())
-      .map(fields =>
-        fields
-          .iterator
-          .zipWithIndex
-          .map { case ((k, t), i) => PField(k, t, i) }
-          .toArray
-      )
-  }
-
-  def preGenStruct(required: Boolean, genFieldType: Gen[PType]): Gen[PStruct] =
-    for (fields <- genFields(required, genFieldType)) yield PCanonicalStruct(fields, required)
-
-  def preGenTuple(required: Boolean, genFieldType: Gen[PType]): Gen[PTuple] =
-    for (fields <- genFields(required, genFieldType))
-      yield PCanonicalTuple(required, fields.map(_.typ): _*)
-
-  private val defaultRequiredGenRatio = 0.2
-
-  def genStruct: Gen[PStruct] = Gen.coin(defaultRequiredGenRatio).flatMap(preGenStruct(_, genArb))
-
-  val genOptionalStruct: Gen[PType] = preGenStruct(required = false, genArb)
-
-  val genRequiredStruct: Gen[PType] = preGenStruct(required = true, genArb)
-
-  val genInsertableStruct: Gen[PStruct] = Gen.coin(defaultRequiredGenRatio).flatMap(required =>
-    if (required)
-      preGenStruct(required = true, genArb)
-    else
-      preGenStruct(required = false, genOptional)
-  )
-
-  def genSized(size: Int, required: Boolean, genPStruct: Gen[PStruct]): Gen[PType] =
-    if (size < 1)
-      Gen.const(PCanonicalStruct.empty(required))
-    else if (size < 2)
-      genScalar(required)
-    else {
-      Gen.frequency(
-        (4, genScalar(required)),
-        (1, genComplexType(required)),
-        (
-          1,
-          genArb.map {
-            PCanonicalArray(_)
-          },
-        ),
-        (
-          1,
-          genArb.map {
-            PCanonicalSet(_)
-          },
-        ),
-        (
-          1,
-          genArb.map {
-            PCanonicalInterval(_)
-          },
-        ),
-        (1, preGenTuple(required, genArb)),
-        (1, Gen.zip(genRequired, genArb).map { case (k, v) => PCanonicalDict(k, v) }),
-        (1, genPStruct.resize(size)),
-      )
-    }
-
-  def preGenArb(required: Boolean, genStruct: Gen[PStruct] = genStruct): Gen[PType] =
-    Gen.sized(genSized(_, required, genStruct))
-
-  def genArb: Gen[PType] = Gen.coin(0.2).flatMap(preGenArb(_))
-
-  val genOptional: Gen[PType] = preGenArb(required = false)
-
-  val genRequired: Gen[PType] = preGenArb(required = true)
-
-  val genInsertable: Gen[PStruct] = genInsertableStruct
-
-  implicit def arbType = Arbitrary(genArb)
 
   def canonical(t: Type, required: Boolean, innerRequired: Boolean): PType = {
     t match {
@@ -397,15 +293,6 @@ object PType {
 }
 
 abstract class PType extends Serializable with Requiredness {
-  self =>
-
-  def genValue(sm: HailStateManager): Gen[Annotation] =
-    if (required) genNonmissingValue(sm)
-    else Gen.nextCoin(0.05).flatMap(isEmpty =>
-      if (isEmpty) Gen.const(null) else genNonmissingValue(sm)
-    )
-
-  def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = virtualType.genNonmissingValue(sm)
 
   def virtualType: Type
 
diff --git a/hail/hail/src/is/hail/types/virtual/TArray.scala b/hail/hail/src/is/hail/types/virtual/TArray.scala
index c36d7706f61..81a5f4e0113 100644
--- a/hail/hail/src/is/hail/types/virtual/TArray.scala
+++ b/hail/hail/src/is/hail/types/virtual/TArray.scala
@@ -2,7 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations.{Annotation, ExtendedOrdering}
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 
 import org.json4s.jackson.JsonMethods
 
@@ -43,9 +42,6 @@ final case class TArray(elementType: Type) extends TContainer {
 
   override def str(a: Annotation): String = JsonMethods.compact(export(a))
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[IndexedSeq[Annotation]] =
-    Gen.buildableOf[Array](elementType.genValue(sm)).map(x => x: IndexedSeq[Annotation])
-
   def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering =
     ExtendedOrdering.iterableOrdering(elementType.ordering(sm), missingEqual)
 
diff --git a/hail/hail/src/is/hail/types/virtual/TBaseStruct.scala b/hail/hail/src/is/hail/types/virtual/TBaseStruct.scala
index 1f6f9e6377a..bb79f152988 100644
--- a/hail/hail/src/is/hail/types/virtual/TBaseStruct.scala
+++ b/hail/hail/src/is/hail/types/virtual/TBaseStruct.scala
@@ -2,7 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.utils._
 
 import org.apache.spark.sql.Row
@@ -95,18 +94,6 @@ abstract class TBaseStruct extends Type {
 
   override def str(a: Annotation): String = JsonMethods.compact(export(a))
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = {
-    if (types.isEmpty) {
-      Gen.const(Annotation.empty)
-    } else
-      Gen.size.flatMap(fuel =>
-        if (types.length > fuel)
-          Gen.uniformSequence(types.map(t => Gen.const(null))).map(a => Annotation(a: _*))
-        else
-          Gen.uniformSequence(types.map(t => t.genValue(sm))).map(a => Annotation(a: _*))
-      )
-  }
-
   override def valuesSimilar(a1: Annotation, a2: Annotation, tolerance: Double, absolute: Boolean)
     : Boolean =
     a1 == a2 || (a1 != null && a2 != null
diff --git a/hail/hail/src/is/hail/types/virtual/TBinary.scala b/hail/hail/src/is/hail/types/virtual/TBinary.scala
index 3751ee2244d..d904f538c41 100644
--- a/hail/hail/src/is/hail/types/virtual/TBinary.scala
+++ b/hail/hail/src/is/hail/types/virtual/TBinary.scala
@@ -2,17 +2,12 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.Arbitrary._
-import is.hail.check.Gen
 
 case object TBinary extends Type {
   def _toPretty = "Binary"
 
   def _typeCheck(a: Any): Boolean = a.isInstanceOf[Array[Byte]]
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    Gen.buildableOf(arbitrary[Byte])
-
   def mkOrdering(sm: HailStateManager, _missingEqual: Boolean = true): ExtendedOrdering =
     ExtendedOrdering.iterableOrdering(new ExtendedOrdering {
       val missingEqual = _missingEqual
diff --git a/hail/hail/src/is/hail/types/virtual/TBoolean.scala b/hail/hail/src/is/hail/types/virtual/TBoolean.scala
index 7eaba727d91..ac5f75cb2cf 100644
--- a/hail/hail/src/is/hail/types/virtual/TBoolean.scala
+++ b/hail/hail/src/is/hail/types/virtual/TBoolean.scala
@@ -2,8 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.Arbitrary._
-import is.hail.check.Gen
 
 case object TBoolean extends Type {
   def _toPretty = "Boolean"
@@ -17,8 +15,6 @@ case object TBoolean extends Type {
 
   def parse(s: String): Annotation = s.toBoolean
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = arbitrary[Boolean]
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering =
     ExtendedOrdering.extendToNull(implicitly[Ordering[Boolean]], missingEqual)
 
diff --git a/hail/hail/src/is/hail/types/virtual/TCall.scala b/hail/hail/src/is/hail/types/virtual/TCall.scala
index 1fcb637bd45..d59bbc0d17e 100644
--- a/hail/hail/src/is/hail/types/virtual/TCall.scala
+++ b/hail/hail/src/is/hail/types/virtual/TCall.scala
@@ -2,7 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.variant.Call
 
 case object TCall extends Type {
@@ -15,8 +14,6 @@ case object TCall extends Type {
 
   def _typeCheck(a: Any): Boolean = a.isInstanceOf[Int]
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = Call.genNonmissingValue
-
   override def str(a: Annotation): String =
     if (a == null) "NA" else Call.toString(a.asInstanceOf[Call])
 
diff --git a/hail/hail/src/is/hail/types/virtual/TDict.scala b/hail/hail/src/is/hail/types/virtual/TDict.scala
index 54e124db563..0a4f4d9c9a7 100644
--- a/hail/hail/src/is/hail/types/virtual/TDict.scala
+++ b/hail/hail/src/is/hail/types/virtual/TDict.scala
@@ -2,7 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations.{Annotation, ExtendedOrdering}
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.utils._
 
 import org.json4s.jackson.JsonMethods
@@ -59,9 +58,6 @@ final case class TDict(keyType: Type, valueType: Type) extends TContainer {
 
   override def str(a: Annotation): String = JsonMethods.compact(export(a))
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    Gen.buildableOf2[Map](Gen.zip(keyType.genValue(sm), valueType.genValue(sm)))
-
   override def valuesSimilar(a1: Annotation, a2: Annotation, tolerance: Double, absolute: Boolean)
     : Boolean =
     a1 == a2 || (a1 != null && a2 != null &&
diff --git a/hail/hail/src/is/hail/types/virtual/TFloat32.scala b/hail/hail/src/is/hail/types/virtual/TFloat32.scala
index b2aaf5776de..81d6784512d 100644
--- a/hail/hail/src/is/hail/types/virtual/TFloat32.scala
+++ b/hail/hail/src/is/hail/types/virtual/TFloat32.scala
@@ -2,8 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.Arbitrary._
-import is.hail.check.Gen
 import is.hail.utils._
 
 case object TFloat32 extends TNumeric {
@@ -19,9 +17,6 @@ case object TFloat32 extends TNumeric {
   override def str(a: Annotation): String =
     if (a == null) "NA" else "%.5e".format(a.asInstanceOf[Float])
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    arbitrary[Double].map(_.toFloat)
-
   override def valuesSimilar(a1: Annotation, a2: Annotation, tolerance: Double, absolute: Boolean)
     : Boolean =
     a1 == a2 || (a1 != null && a2 != null && {
diff --git a/hail/hail/src/is/hail/types/virtual/TFloat64.scala b/hail/hail/src/is/hail/types/virtual/TFloat64.scala
index 7a8f78a7826..20bc1843611 100644
--- a/hail/hail/src/is/hail/types/virtual/TFloat64.scala
+++ b/hail/hail/src/is/hail/types/virtual/TFloat64.scala
@@ -2,8 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.Arbitrary._
-import is.hail.check.Gen
 import is.hail.utils._
 
 case object TFloat64 extends TNumeric {
@@ -19,8 +17,6 @@ case object TFloat64 extends TNumeric {
   override def str(a: Annotation): String =
     if (a == null) "NA" else "%.5e".format(a.asInstanceOf[Double])
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = arbitrary[Double]
-
   override def valuesSimilar(a1: Annotation, a2: Annotation, tolerance: Double, absolute: Boolean)
     : Boolean =
     a1 == a2 || (a1 != null && a2 != null && {
diff --git a/hail/hail/src/is/hail/types/virtual/TInt32.scala b/hail/hail/src/is/hail/types/virtual/TInt32.scala
index 9c33fef567a..64ce28795a2 100644
--- a/hail/hail/src/is/hail/types/virtual/TInt32.scala
+++ b/hail/hail/src/is/hail/types/virtual/TInt32.scala
@@ -2,8 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.Arbitrary._
-import is.hail.check.Gen
 
 case object TInt32 extends TIntegral {
   def _toPretty = "Int32"
@@ -13,8 +11,6 @@ case object TInt32 extends TIntegral {
 
   def _typeCheck(a: Any): Boolean = a.isInstanceOf[Int]
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = arbitrary[Int]
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering =
     ExtendedOrdering.extendToNull(implicitly[Ordering[Int]], missingEqual)
 
diff --git a/hail/hail/src/is/hail/types/virtual/TInt64.scala b/hail/hail/src/is/hail/types/virtual/TInt64.scala
index d1557cea240..4979bf53117 100644
--- a/hail/hail/src/is/hail/types/virtual/TInt64.scala
+++ b/hail/hail/src/is/hail/types/virtual/TInt64.scala
@@ -2,8 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.Arbitrary._
-import is.hail.check.Gen
 
 case object TInt64 extends TIntegral {
   def _toPretty = "Int64"
@@ -13,8 +11,6 @@ case object TInt64 extends TIntegral {
 
   def _typeCheck(a: Any): Boolean = a.isInstanceOf[Long]
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = arbitrary[Long]
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering =
     ExtendedOrdering.extendToNull(implicitly[Ordering[Long]], missingEqual)
 
diff --git a/hail/hail/src/is/hail/types/virtual/TInterval.scala b/hail/hail/src/is/hail/types/virtual/TInterval.scala
index 2761b0944a6..50c1a1394ab 100644
--- a/hail/hail/src/is/hail/types/virtual/TInterval.scala
+++ b/hail/hail/src/is/hail/types/virtual/TInterval.scala
@@ -1,8 +1,7 @@
 package is.hail.types.virtual
 
-import is.hail.annotations.{Annotation, ExtendedOrdering}
+import is.hail.annotations.ExtendedOrdering
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.utils.{FastSeq, Interval}
 
 case class TInterval(pointType: Type) extends Type {
@@ -28,9 +27,6 @@ case class TInterval(pointType: Type) extends Type {
     pointType.typeCheck(i.start) && pointType.typeCheck(i.end)
   }
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    Interval.gen(pointType.ordering(sm), pointType.genValue(sm))
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering =
     Interval.ordering(pointType.ordering(sm), startPrimary = true, missingEqual)
 
diff --git a/hail/hail/src/is/hail/types/virtual/TLocus.scala b/hail/hail/src/is/hail/types/virtual/TLocus.scala
index 4dd1c9986d6..fba034f4a10 100644
--- a/hail/hail/src/is/hail/types/virtual/TLocus.scala
+++ b/hail/hail/src/is/hail/types/virtual/TLocus.scala
@@ -2,7 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check._
 import is.hail.utils._
 import is.hail.variant._
 
@@ -34,9 +33,6 @@ case class TLocus(rgName: String) extends Type {
 
   def _typeCheck(a: Any): Boolean = a.isInstanceOf[Locus]
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    Locus.gen(sm.referenceGenomes(rgName))
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean = true): ExtendedOrdering =
     sm.referenceGenomes(rgName).extendedLocusOrdering
 
diff --git a/hail/hail/src/is/hail/types/virtual/TNDArray.scala b/hail/hail/src/is/hail/types/virtual/TNDArray.scala
index 09873847a05..94e9d35c55e 100644
--- a/hail/hail/src/is/hail/types/virtual/TNDArray.scala
+++ b/hail/hail/src/is/hail/types/virtual/TNDArray.scala
@@ -2,7 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations.{Annotation, ExtendedOrdering, NDArray}
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.expr.{Nat, NatBase}
 
 object TNDArray {
@@ -111,8 +110,6 @@ final case class TNDArray(elementType: Type, nDimsBase: NatBase) extends Type {
     case _ => false
   }
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering = null
 
   lazy val shapeType: TTuple = TTuple(Array.fill(nDims)(TInt64): _*)
diff --git a/hail/hail/src/is/hail/types/virtual/TRNGState.scala b/hail/hail/src/is/hail/types/virtual/TRNGState.scala
index 268e04d9178..7e33f8427a9 100644
--- a/hail/hail/src/is/hail/types/virtual/TRNGState.scala
+++ b/hail/hail/src/is/hail/types/virtual/TRNGState.scala
@@ -1,8 +1,6 @@
 package is.hail.types.virtual
 
-import is.hail.annotations.Annotation
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 
 case object TRNGState extends Type {
   override def _toPretty = "RNGState"
@@ -10,7 +8,6 @@ case object TRNGState extends Type {
   override def pyString(sb: StringBuilder): Unit =
     sb.append("rng_state")
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
   def _typeCheck(a: Any): Boolean = ???
 
   def mkOrdering(sm: HailStateManager, missingEqual: Boolean)
diff --git a/hail/hail/src/is/hail/types/virtual/TSet.scala b/hail/hail/src/is/hail/types/virtual/TSet.scala
index 3faf59213fb..9d126d827d1 100644
--- a/hail/hail/src/is/hail/types/virtual/TSet.scala
+++ b/hail/hail/src/is/hail/types/virtual/TSet.scala
@@ -2,7 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations.{Annotation, ExtendedOrdering}
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 
 import org.json4s.jackson.JsonMethods
 
@@ -46,9 +45,6 @@ final case class TSet(elementType: Type) extends TContainer {
 
   override def str(a: Annotation): String = JsonMethods.compact(export(a))
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    Gen.buildableOf[Set](elementType.genValue(sm))
-
   override def valueSubsetter(subtype: Type): Any => Any = {
     assert(elementType == subtype.asInstanceOf[TSet].elementType)
     identity
diff --git a/hail/hail/src/is/hail/types/virtual/TStream.scala b/hail/hail/src/is/hail/types/virtual/TStream.scala
index f9ff78a6724..ee9678ca2d1 100644
--- a/hail/hail/src/is/hail/types/virtual/TStream.scala
+++ b/hail/hail/src/is/hail/types/virtual/TStream.scala
@@ -2,7 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations.{Annotation, ExtendedOrdering}
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 
 import org.json4s.jackson.JsonMethods
 
@@ -38,9 +37,6 @@ final case class TStream(elementType: Type) extends TIterable {
 
   override def isRealizable = false
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
-    throw new UnsupportedOperationException("Streams don't have associated annotations.")
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering =
     throw new UnsupportedOperationException("Stream comparison is currently undefined.")
 
diff --git a/hail/hail/src/is/hail/types/virtual/TString.scala b/hail/hail/src/is/hail/types/virtual/TString.scala
index 2805f809b79..637cbafd340 100644
--- a/hail/hail/src/is/hail/types/virtual/TString.scala
+++ b/hail/hail/src/is/hail/types/virtual/TString.scala
@@ -2,8 +2,6 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.Arbitrary._
-import is.hail.check.Gen
 
 case object TString extends Type {
   def _toPretty = "String"
@@ -15,8 +13,6 @@ case object TString extends Type {
 
   def _typeCheck(a: Any): Boolean = a.isInstanceOf[String]
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = arbitrary[String]
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering =
     ExtendedOrdering.extendToNull(implicitly[Ordering[String]], missingEqual)
 
diff --git a/hail/hail/src/is/hail/types/virtual/TUnion.scala b/hail/hail/src/is/hail/types/virtual/TUnion.scala
index 35e65dd8838..ba3c24c9ec2 100644
--- a/hail/hail/src/is/hail/types/virtual/TUnion.scala
+++ b/hail/hail/src/is/hail/types/virtual/TUnion.scala
@@ -1,8 +1,7 @@
 package is.hail.types.virtual
 
-import is.hail.annotations.{Annotation, ExtendedOrdering}
+import is.hail.annotations.ExtendedOrdering
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.expr.ir.IRParser
 import is.hail.utils._
 
@@ -123,8 +122,6 @@ final case class TUnion(cases: IndexedSeq[Case]) extends Type {
     }
   }
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering = ???
 
   override def isIsomorphicTo(t: Type): Boolean =
diff --git a/hail/hail/src/is/hail/types/virtual/TVariable.scala b/hail/hail/src/is/hail/types/virtual/TVariable.scala
index 5cd3be972df..a395ab02c26 100644
--- a/hail/hail/src/is/hail/types/virtual/TVariable.scala
+++ b/hail/hail/src/is/hail/types/virtual/TVariable.scala
@@ -1,8 +1,7 @@
 package is.hail.types.virtual
 
-import is.hail.annotations.{Annotation, ExtendedOrdering}
+import is.hail.annotations.ExtendedOrdering
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 import is.hail.types.Box
 
 import scala.collection.mutable
@@ -70,8 +69,6 @@ final case class TVariable(name: String, cond: String = null) extends Type {
     t
   }
 
-  override def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering = null
 
   override def isIsomorphicTo(t: Type): Boolean =
diff --git a/hail/hail/src/is/hail/types/virtual/TVoid.scala b/hail/hail/src/is/hail/types/virtual/TVoid.scala
index 0c11cb56d9b..ff04792d562 100644
--- a/hail/hail/src/is/hail/types/virtual/TVoid.scala
+++ b/hail/hail/src/is/hail/types/virtual/TVoid.scala
@@ -1,8 +1,7 @@
 package is.hail.types.virtual
 
-import is.hail.annotations.{Annotation, ExtendedOrdering}
+import is.hail.annotations.ExtendedOrdering
 import is.hail.backend.HailStateManager
-import is.hail.check.Gen
 
 case object TVoid extends Type {
   override def _toPretty = "Void"
@@ -10,8 +9,6 @@ case object TVoid extends Type {
   override def pyString(sb: StringBuilder): Unit =
     sb.append("void")
 
-  def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
-
   override def mkOrdering(sm: HailStateManager, missingEqual: Boolean): ExtendedOrdering = null
 
   override def _typeCheck(a: Any): Boolean = a.isInstanceOf[Unit]
diff --git a/hail/hail/src/is/hail/types/virtual/Type.scala b/hail/hail/src/is/hail/types/virtual/Type.scala
index 89212ddeb42..a2497422150 100644
--- a/hail/hail/src/is/hail/types/virtual/Type.scala
+++ b/hail/hail/src/is/hail/types/virtual/Type.scala
@@ -2,12 +2,10 @@ package is.hail.types.virtual
 
 import is.hail.annotations._
 import is.hail.backend.HailStateManager
-import is.hail.check.{Arbitrary, Gen}
 import is.hail.expr.{JSONAnnotationImpex, SparkAnnotationImpex}
 import is.hail.expr.ir._
 import is.hail.utils
 import is.hail.utils._
-import is.hail.variant.ReferenceGenome
 
 import org.apache.spark.sql.types.DataType
 import org.json4s.{CustomSerializer, JValue}
@@ -20,96 +18,6 @@ class TypeSerializer extends CustomSerializer[Type](_ =>
       )
     )
 
-object Type {
-  def genScalar(): Gen[Type] =
-    Gen.oneOf(TBoolean, TInt32, TInt64, TFloat32,
-      TFloat64, TString, TCall)
-
-  def genComplexType(): Gen[Type] = {
-    val rgDependents = ReferenceGenome.hailReferences.toArray.map(TLocus(_))
-    val others = Array(TCall)
-    Gen.oneOfSeq(rgDependents ++ others)
-  }
-
-  def genFields(genFieldType: Gen[Type]): Gen[Array[Field]] = {
-    Gen.buildableOf[Array](
-      Gen.zip(Gen.identifier, genFieldType)
-    )
-      .filter(fields => fields.map(_._1).areDistinct())
-      .map(fields =>
-        fields
-          .iterator
-          .zipWithIndex
-          .map { case ((k, t), i) => Field(k, t, i) }
-          .toArray
-      )
-  }
-
-  def preGenStruct(genFieldType: Gen[Type]): Gen[TStruct] =
-    for (fields <- genFields(genFieldType)) yield TStruct(fields)
-
-  def preGenTuple(genFieldType: Gen[Type]): Gen[TTuple] =
-    for (fields <- genFields(genFieldType)) yield TTuple(fields.map(_.typ): _*)
-
-  private val defaultRequiredGenRatio = 0.2
-  def genStruct: Gen[TStruct] = Gen.coin(defaultRequiredGenRatio).flatMap(c => preGenStruct(genArb))
-
-  def genSized(size: Int, genTStruct: Gen[TStruct]): Gen[Type] =
-    if (size < 1)
-      Gen.const(TStruct.empty)
-    else if (size < 2)
-      genScalar()
-    else {
-      Gen.frequency(
-        (4, genScalar()),
-        (1, genComplexType()),
-        (
-          1,
-          genArb.map {
-            TArray(_)
-          },
-        ),
-        (
-          1,
-          genArb.map {
-            TSet(_)
-          },
-        ),
-        (
-          1,
-          genArb.map {
-            TInterval(_)
-          },
-        ),
-        (1, preGenTuple(genArb)),
-        (1, Gen.zip(genRequired, genArb).map { case (k, v) => TDict(k, v) }),
-        (1, genTStruct.resize(size)),
-      )
-    }
-
-  def preGenArb(genStruct: Gen[TStruct] = genStruct): Gen[Type] =
-    Gen.sized(genSized(_, genStruct))
-
-  def genArb: Gen[Type] = preGenArb()
-
-  val genOptional: Gen[Type] = preGenArb()
-
-  val genRequired: Gen[Type] = preGenArb()
-
-  def genWithValue(sm: HailStateManager): Gen[(Type, Annotation)] = for {
-    s <- Gen.size
-    // prefer smaller type and bigger values
-    fraction <- Gen.choose(0.1, 0.3)
-    x = (fraction * s).toInt
-    y = s - x
-    t <- Type.genStruct.resize(x)
-    v <- t.genValue(sm).resize(y)
-  } yield (t, v)
-
-  implicit def arbType: Arbitrary[Type] =
-    Arbitrary(genArb)
-}
-
 abstract class Type extends VType with Serializable {
 
   def children: IndexedSeq[Type] = FastSeq()
@@ -177,11 +85,6 @@ abstract class Type extends VType with Serializable {
   override def toJSON: JValue =
     JString(toString)
 
-  def genNonmissingValue(sm: HailStateManager): Gen[Annotation]
-
-  def genValue(sm: HailStateManager): Gen[Annotation] =
-    Gen.nextCoin(0.05).flatMap(isEmpty => if (isEmpty) Gen.const(null) else genNonmissingValue(sm))
-
   def isRealizable: Boolean = children.forall(_.isRealizable)
 
   /* compare values for equality, but compare Float and Double values by the absolute value of their
diff --git a/hail/hail/src/is/hail/utils/Interval.scala b/hail/hail/src/is/hail/utils/Interval.scala
index 6ffa27745d4..3beaa10b34d 100644
--- a/hail/hail/src/is/hail/utils/Interval.scala
+++ b/hail/hail/src/is/hail/utils/Interval.scala
@@ -1,7 +1,6 @@
 package is.hail.utils
 
 import is.hail.annotations._
-import is.hail.check._
 import is.hail.types.virtual.TBoolean
 
 import org.apache.spark.sql.Row
@@ -208,16 +207,6 @@ object Interval {
       IntervalEndpoint(end, if (includesEnd) 1 else -1),
     )
 
-  def gen[P](pord: ExtendedOrdering, pgen: Gen[P]): Gen[Interval] =
-    Gen.zip(pgen, pgen, Gen.coin(), Gen.coin())
-      .filter { case (x, y, s, e) => pord.compare(x, y) != 0 || (s && e) }
-      .map { case (x, y, s, e) =>
-        if (pord.compare(x, y) < 0)
-          Interval(x, y, s, e)
-        else
-          Interval(y, x, s, e)
-      }
-
   def ordering(pord: ExtendedOrdering, startPrimary: Boolean, _missingEqual: Boolean = true)
     : ExtendedOrdering = new ExtendedOrdering {
     val missingEqual = _missingEqual
diff --git a/hail/hail/src/is/hail/utils/package.scala b/hail/hail/src/is/hail/utils/package.scala
index 201cf59aa75..8b6affd9801 100644
--- a/hail/hail/src/is/hail/utils/package.scala
+++ b/hail/hail/src/is/hail/utils/package.scala
@@ -1,7 +1,6 @@
 package is.hail
 
 import is.hail.annotations.ExtendedOrdering
-import is.hail.check.Gen
 import is.hail.expr.ir.ByteArrayBuilder
 import is.hail.io.fs.{FS, FileListEntry}
 
@@ -324,8 +323,6 @@ package object utils
   def flushDouble(a: Double): Double =
     if (math.abs(a) < java.lang.Double.MIN_NORMAL) 0.0 else a
 
-  def genBase: Gen[Char] = Gen.oneOf('A', 'C', 'T', 'G')
-
   def getPartNumber(fname: String): Int = {
     val partRegex = """.*/?part-(\d+).*""".r
 
@@ -346,11 +343,6 @@ package object utils
     }
   }
 
-  // ignore size; atomic, like String
-  def genDNAString: Gen[String] = Gen.stringOf(genBase)
-    .resize(12)
-    .filter(s => !s.isEmpty)
-
   def prettyIdentifier(str: String): String =
     if (str.matches("""[_a-zA-Z]\w*"""))
       str
diff --git a/hail/hail/src/is/hail/variant/Call.scala b/hail/hail/src/is/hail/variant/Call.scala
index 400d9e63559..e542a325bab 100644
--- a/hail/hail/src/is/hail/variant/Call.scala
+++ b/hail/hail/src/is/hail/variant/Call.scala
@@ -1,6 +1,5 @@
 package is.hail.variant
 
-import is.hail.check.Gen
 import is.hail.expr.Parser
 import is.hail.utils._
 
@@ -468,53 +467,4 @@ object Call extends Serializable {
       }
     }
   }
-
-  def check(c: Call, nAlleles: Int): Unit = {
-    (ploidy(c): @switch) match {
-      case 0 =>
-      case 1 =>
-        val a = alleleByIndex(c, 0)
-        assert(a >= 0 && a < nAlleles)
-      case 2 =>
-        val nGenotypes = triangle(nAlleles)
-        val udtn =
-          if (isPhased(c)) {
-            val p = allelePair(c)
-            unphasedDiploidGtIndex(Call2(AllelePair.j(p), AllelePair.k(p)))
-          } else
-            unphasedDiploidGtIndex(c)
-        assert(
-          udtn < nGenotypes,
-          s"Invalid call found '${c.toString}' for number of alleles equal to '$nAlleles'.",
-        )
-      case _ =>
-        alleles(c).foreach(a => assert(a >= 0 && a < nAlleles))
-    }
-  }
-
-  def gen(
-    nAlleles: Int,
-    ploidyGen: Gen[Int] = Gen.choose(0, 2),
-    phasedGen: Gen[Boolean] = Gen.nextCoin(0.5),
-  ): Gen[Call] = for {
-    ploidy <- ploidyGen
-    phased <- phasedGen
-    alleles <- Gen.buildableOfN[Array](ploidy, Gen.choose(0, nAlleles - 1))
-  } yield {
-    val c = CallN(alleles, phased)
-    check(c, nAlleles)
-    c
-  }
-
-  def genUnphasedDiploid(nAlleles: Int): Gen[Call] = gen(nAlleles, Gen.const(2), Gen.const(false))
-
-  def genPhasedDiploid(nAlleles: Int): Gen[Call] = gen(nAlleles, Gen.const(2), Gen.const(true))
-
-  def genNonmissingValue: Gen[Call] = for {
-    nAlleles <- Gen.choose(2, 5)
-    c <- gen(nAlleles)
-  } yield {
-    check(c, nAlleles)
-    c
-  }
 }
diff --git a/hail/hail/src/is/hail/variant/Genotype.scala b/hail/hail/src/is/hail/variant/Genotype.scala
index 3acf5989c6c..d59ae0241ad 100644
--- a/hail/hail/src/is/hail/variant/Genotype.scala
+++ b/hail/hail/src/is/hail/variant/Genotype.scala
@@ -1,9 +1,7 @@
 package is.hail.variant
 
 import is.hail.annotations.Annotation
-import is.hail.check.Gen
 import is.hail.types.virtual.{TArray, TCall, TInt32, TStruct}
-import is.hail.utils._
 
 import org.apache.spark.sql.Row
 
@@ -240,96 +238,4 @@ object Genotype {
     else
       diploidGtIndex(i, j)
 
-  def genExtremeNonmissing(nAlleles: Int): Gen[Annotation] = {
-    val m = Int.MaxValue / (nAlleles + 1)
-    val nGenotypes = triangle(nAlleles)
-    val gg = for {
-      c: Option[Call] <- Gen.option(Call.genUnphasedDiploid(nAlleles))
-      ad <- Gen.option(Gen.buildableOfN[Array](nAlleles, Gen.choose(0, m)))
-      dp <- Gen.option(Gen.choose(0, m))
-      gq <- Gen.option(Gen.choose(0, 10000))
-      pl <- Gen.oneOfGen(
-        Gen.option(Gen.buildableOfN[Array](nGenotypes, Gen.choose(0, m))),
-        Gen.option(Gen.buildableOfN[Array](nGenotypes, Gen.choose(0, 100))),
-      )
-    } yield {
-      c.foreach(c => pl.foreach(pla => pla(Call.unphasedDiploidGtIndex(c)) = 0))
-      pl.foreach { pla =>
-        val m = pla.min
-        var i = 0
-        while (i < pla.length) {
-          pla(i) -= m
-          i += 1
-        }
-      }
-      val g = Annotation(
-        c.orNull,
-        ad.map(a => a: IndexedSeq[Int]).orNull,
-        dp.map(_ + ad.map(_.sum).getOrElse(0)).orNull,
-        gq.orNull,
-        pl.map(a => a: IndexedSeq[Int]).orNull,
-      )
-      g
-    }
-    gg
-  }
-
-  def genExtreme(nAlleles: Int): Gen[Annotation] =
-    Gen.frequency(
-      (100, genExtremeNonmissing(nAlleles)),
-      (1, Gen.const(null)),
-    )
-
-  def genRealisticNonmissing(nAlleles: Int): Gen[Annotation] = {
-    val nGenotypes = triangle(nAlleles)
-    val gg = for {
-      callRate <- Gen.choose(0d, 1d)
-      alleleFrequencies <-
-        Gen.buildableOfN[Array](nAlleles, Gen.choose(1e-6, 1d)) // avoid divison by 0
-          .map { rawWeights =>
-            val sum = rawWeights.sum
-            rawWeights.map(_ / sum)
-          }
-      c <- Gen.option(
-        Gen.zip(Gen.chooseWithWeights(alleleFrequencies), Gen.chooseWithWeights(alleleFrequencies))
-          .map { case (gti, gtj) => Call2(gti, gtj) },
-        callRate,
-      )
-      ad <- Gen.option(Gen.buildableOfN[Array](nAlleles, Gen.choose(0, 50)))
-      dp <- Gen.choose(0, 30).map(d => ad.map(o => o.sum + d))
-      pl <- Gen.option(Gen.buildableOfN[Array](nGenotypes, Gen.choose(0, 1000)).map { arr =>
-        c match {
-          case Some(x) =>
-            arr(Call.unphasedDiploidGtIndex(x)) = 0
-            arr
-          case None =>
-            val min = arr.min
-            arr.map(_ - min)
-        }
-      })
-      gq <- Gen.choose(-30, 30).map(i => pl.map(pls => math.max(0, gqFromPL(pls) + i)))
-    } yield Annotation(c.orNull, ad.map(a => a: IndexedSeq[Int]).orNull, dp.orNull, gq.orNull, pl.map(a => a: IndexedSeq[Int]).orNull)
-    gg
-  }
-
-  def genRealistic(nAlleles: Int): Gen[Annotation] =
-    Gen.frequency(
-      (100, genRealisticNonmissing(nAlleles)),
-      (1, Gen.const(null)),
-    )
-
-  def genGenericCallAndProbabilitiesGenotype(nAlleles: Int): Gen[Annotation] = {
-    val nGenotypes = triangle(nAlleles)
-    val gg = for (gp <- Gen.option(Gen.partition(nGenotypes, 32768))) yield {
-      val c = gp.flatMap(a => Option(uniqueMaxIndex(a))).map(Call2.fromUnphasedDiploidGtIndex(_))
-      Row(
-        c.orNull,
-        gp.map(gpx => gpx.map(p => p.toDouble / 32768): IndexedSeq[Double]).orNull,
-      )
-    }
-    Gen.frequency(
-      (100, gg),
-      (1, Gen.const(null)),
-    )
-  }
 }
diff --git a/hail/hail/src/is/hail/variant/Locus.scala b/hail/hail/src/is/hail/variant/Locus.scala
index da7dc169e7b..0dce76a33c3 100644
--- a/hail/hail/src/is/hail/variant/Locus.scala
+++ b/hail/hail/src/is/hail/variant/Locus.scala
@@ -1,7 +1,6 @@
 package is.hail.variant
 
 import is.hail.annotations.Annotation
-import is.hail.check.Gen
 import is.hail.expr.Parser
 import is.hail.utils._
 
@@ -34,11 +33,6 @@ object Locus {
   def fromRow(r: Row): Locus =
     Locus(r.getAs[String](0), r.getInt(1))
 
-  def gen(rg: ReferenceGenome): Gen[Locus] = for {
-    (contig, length) <- Contig.gen(rg)
-    pos <- Gen.choose(1, length)
-  } yield Locus(contig, pos)
-
   def parse(str: String, rg: ReferenceGenome): Locus = {
     val elts = str.split(":")
     val size = elts.length
diff --git a/hail/hail/src/is/hail/variant/ReferenceGenome.scala b/hail/hail/src/is/hail/variant/ReferenceGenome.scala
index 1aa5a14d526..88e07e04073 100644
--- a/hail/hail/src/is/hail/variant/ReferenceGenome.scala
+++ b/hail/hail/src/is/hail/variant/ReferenceGenome.scala
@@ -2,7 +2,6 @@ package is.hail.variant
 
 import is.hail.annotations.ExtendedOrdering
 import is.hail.backend.ExecuteContext
-import is.hail.check.Gen
 import is.hail.expr.{
   JSONExtractContig, JSONExtractIntervalLocus, JSONExtractReferenceGenome, Parser,
 }
@@ -607,33 +606,6 @@ object ReferenceGenome {
     Integer.compare(l1.position, l2.position)
   }
 
-  def gen: Gen[ReferenceGenome] =
-    for {
-      name <- Gen.identifier.filter(!ReferenceGenome.hailReferences.contains(_))
-      nContigs <- Gen.choose(3, 10)
-      contigs <- Gen.distinctBuildableOfN[Array](nContigs, Gen.identifier)
-      lengths <- Gen.buildableOfN[Array](nContigs, Gen.choose(1000000, 500000000))
-      contigsIndex = contigs.zip(lengths).toMap
-      xContig <- Gen.oneOfSeq(contigs)
-      parXA <- Gen.choose(0, contigsIndex(xContig))
-      parXB <- Gen.choose(0, contigsIndex(xContig))
-      yContig <- Gen.oneOfSeq(contigs) if yContig != xContig
-      parYA <- Gen.choose(0, contigsIndex(yContig))
-      parYB <- Gen.choose(0, contigsIndex(yContig))
-      mtContig <- Gen.oneOfSeq(contigs) if mtContig != xContig && mtContig != yContig
-    } yield ReferenceGenome(
-      name,
-      contigs,
-      contigs.zip(lengths).toMap,
-      Set(xContig),
-      Set(yContig),
-      Set(mtContig),
-      Array(
-        (Locus(xContig, math.min(parXA, parXB)), Locus(xContig, math.max(parXA, parXB))),
-        (Locus(yContig, math.min(parYA, parYB)), Locus(yContig, math.max(parYA, parYB))),
-      ),
-    )
-
   def apply(
     name: String,
     contigs: Array[String],
diff --git a/hail/hail/src/is/hail/variant/VariantMethods.scala b/hail/hail/src/is/hail/variant/VariantMethods.scala
index 96f5cc016bb..63cd4d2c792 100644
--- a/hail/hail/src/is/hail/variant/VariantMethods.scala
+++ b/hail/hail/src/is/hail/variant/VariantMethods.scala
@@ -1,13 +1,7 @@
 package is.hail.variant
 
-import is.hail.annotations.Annotation
-import is.hail.check.Gen
 import is.hail.utils._
 
-object Contig {
-  def gen(rg: ReferenceGenome): Gen[(String, Int)] = Gen.oneOfSeq(rg.lengths.toSeq)
-}
-
 object VariantMethods {
 
   def parse(str: String, rg: ReferenceGenome): (Locus, IndexedSeq[String]) = {
@@ -70,48 +64,3 @@ object VariantMethods {
     }
   }
 }
-
-object VariantSubgen {
-  def random(rg: ReferenceGenome): VariantSubgen = VariantSubgen(
-    contigGen = Contig.gen(rg),
-    nAllelesGen = Gen.frequency((5, Gen.const(2)), (1, Gen.choose(2, 10))),
-    refGen = genDNAString,
-    altGen = Gen.frequency((10, genDNAString), (1, Gen.const("*"))),
-  )
-
-  def plinkCompatible(rg: ReferenceGenome): VariantSubgen = {
-    val r = random(rg)
-    val compatible = (1 until 22).map(_.toString).toSet
-    r.copy(
-      contigGen = r.contigGen.filter { case (contig, _) =>
-        compatible.contains(contig)
-      }
-    )
-  }
-
-  def biallelic(rg: ReferenceGenome): VariantSubgen = random(rg).copy(nAllelesGen = Gen.const(2))
-
-  def plinkCompatibleBiallelic(rg: ReferenceGenome): VariantSubgen =
-    plinkCompatible(rg).copy(nAllelesGen = Gen.const(2))
-}
-
-case class VariantSubgen(
-  contigGen: Gen[(String, Int)],
-  nAllelesGen: Gen[Int],
-  refGen: Gen[String],
-  altGen: Gen[String],
-) {
-
-  def genLocusAlleles: Gen[Annotation] =
-    for {
-      (contig, length) <- contigGen
-      start <- Gen.choose(1, length)
-      nAlleles <- nAllelesGen
-      ref <- refGen
-      altAlleles <- Gen.distinctBuildableOfN[Array](
-        nAlleles - 1,
-        altGen,
-      )
-        .filter(!_.contains(ref))
-    } yield Annotation(Locus(contig, start), (ref +: altAlleles).toFastSeq)
-}
diff --git a/hail/hail/test/src/is/hail/annotations/StagedConstructorSuite.scala b/hail/hail/test/src/is/hail/annotations/StagedConstructorSuite.scala
index 8acfb0089c4..3c65bc1042e 100644
--- a/hail/hail/test/src/is/hail/annotations/StagedConstructorSuite.scala
+++ b/hail/hail/test/src/is/hail/annotations/StagedConstructorSuite.scala
@@ -2,6 +2,7 @@ package is.hail.annotations
 
 import is.hail.HailSuite
 import is.hail.asm4s._
+import is.hail.check.Arbitrary.arbitrary
 import is.hail.check.{Gen, Prop}
 import is.hail.expr.ir.{EmitCode, EmitFunctionBuilder, IEmitCode, RequirednessSuite}
 import is.hail.types.physical._
@@ -10,7 +11,6 @@ import is.hail.types.physical.stypes.interfaces._
 import is.hail.types.physical.stypes.primitives.SInt32Value
 import is.hail.types.virtual._
 import is.hail.utils._
-
 import org.apache.spark.sql.Row
 import org.testng.annotations.Test
 
@@ -482,10 +482,11 @@ class StagedConstructorSuite extends HailSuite {
   }
 
   @Test def testDeepCopy(): Unit = {
-    val g = Type.genStruct
-      .flatMap(t => Gen.zip(Gen.const(t), t.genValue(sm)))
-      .filter { case (_, a) => a != null }
-      .map { case (t, a) => (PType.canonical(t).asInstanceOf[PStruct], a) }
+    val g = for {
+      tstruct <- arbitrary[TStruct]
+      struct <- genVal(tstruct)
+      if struct != null
+    } yield (PType.canonical(tstruct), struct)
 
     val p = Prop.forAll(g) { case (t, a) =>
       assert(t.virtualType.typeCheck(a))
diff --git a/hail/hail/test/src/is/hail/annotations/UnsafeSuite.scala b/hail/hail/test/src/is/hail/annotations/UnsafeSuite.scala
index 81a2a82e3a7..dd5d5b4e1e6 100644
--- a/hail/hail/test/src/is/hail/annotations/UnsafeSuite.scala
+++ b/hail/hail/test/src/is/hail/annotations/UnsafeSuite.scala
@@ -2,7 +2,6 @@ package is.hail.annotations
 
 import is.hail.HailSuite
 import is.hail.backend.ExecuteContext
-import is.hail.check._
 import is.hail.io._
 import is.hail.rvd.AbstractRVDSpec
 import is.hail.types.physical._
diff --git a/hail/hail/src/is/hail/check/Arbitrary.scala b/hail/hail/test/src/is/hail/check/Arbitrary.scala
similarity index 100%
rename from hail/hail/src/is/hail/check/Arbitrary.scala
rename to hail/hail/test/src/is/hail/check/Arbitrary.scala
diff --git a/hail/hail/src/is/hail/check/Gen.scala b/hail/hail/test/src/is/hail/check/Gen.scala
similarity index 96%
rename from hail/hail/src/is/hail/check/Gen.scala
rename to hail/hail/test/src/is/hail/check/Gen.scala
index ae157bf802a..be6a9f8eb94 100644
--- a/hail/hail/src/is/hail/check/Gen.scala
+++ b/hail/hail/test/src/is/hail/check/Gen.scala
@@ -537,36 +537,26 @@ object Gen {
 
   def sized[T](f: (Int) => Gen[T]): Gen[T] = Gen((p: Parameters) => f(p.size)(p))
 
-  def applyGen[T, S](gf: Gen[(T) => S], gx: Gen[T]): Gen[S] = Gen { p =>
+  def applyGen[T, S](gf: Gen[T => S], gx: Gen[T]): Gen[S] = Gen { p =>
     val f = gf(p)
     val x = gx(p)
     f(x)
   }
 }
 
-class Gen[+T](val gen: (Parameters) => T) extends AnyVal {
-
-  def apply(p: Parameters): T = gen(p)
+class Gen[+T](val apply: Parameters => T) extends AnyVal {
 
   def sample(): T = apply(Parameters.default)
 
-  def map[U](f: (T) => U): Gen[U] = Gen(p => f(apply(p)))
+  def map[U](f: T => U): Gen[U] = Gen(p => f(apply(p)))
 
-  def flatMap[U](f: (T) => Gen[U]): Gen[U] = Gen(p => f(apply(p))(p))
+  def flatMap[U](f: T => Gen[U]): Gen[U] = Gen(p => f(apply(p))(p))
 
   def resize(newSize: Int): Gen[T] = Gen((p: Parameters) => apply(p.copy(size = newSize)))
+  
+  def withFilter(f: T => Boolean): Gen[T] =
+    Gen((p: Parameters) => Stream.continually(apply(p)).takeWhile(f).head)
 
-  // FIXME should be non-strict
-  def withFilter(f: (T) => Boolean): Gen[T] = Gen { (p: Parameters) =>
-    var x = apply(p)
-    var i = 0
-    while (!f(x)) {
-      assert(i < 100)
-      x = apply(p)
-      i += 1
-    }
-    x
-  }
-
-  def filter(f: (T) => Boolean): Gen[T] = withFilter(f)
+  def filter(f: T => Boolean): Gen[T] = 
+    withFilter(f)
 }
diff --git a/hail/hail/src/is/hail/check/Prop.scala b/hail/hail/test/src/is/hail/check/Prop.scala
similarity index 100%
rename from hail/hail/src/is/hail/check/Prop.scala
rename to hail/hail/test/src/is/hail/check/Prop.scala
diff --git a/hail/hail/test/src/is/hail/io/IndexBTreeSuite.scala b/hail/hail/test/src/is/hail/io/IndexBTreeSuite.scala
index 4682309ba0b..2a1690962c9 100644
--- a/hail/hail/test/src/is/hail/io/IndexBTreeSuite.scala
+++ b/hail/hail/test/src/is/hail/io/IndexBTreeSuite.scala
@@ -1,8 +1,6 @@
 package is.hail.io
 
 import is.hail.HailSuite
-import is.hail.check.Gen._
-import is.hail.check.Prop._
 import is.hail.check.Properties
 
 import org.testng.annotations.Test
diff --git a/hail/hail/test/src/is/hail/linalg/BlockMatrixSuite.scala b/hail/hail/test/src/is/hail/linalg/BlockMatrixSuite.scala
index e32d0c7038e..04a3a8387f4 100644
--- a/hail/hail/test/src/is/hail/linalg/BlockMatrixSuite.scala
+++ b/hail/hail/test/src/is/hail/linalg/BlockMatrixSuite.scala
@@ -10,8 +10,11 @@ import is.hail.expr.ir.defs.{GetField, TableCollect}
 import is.hail.linalg.BlockMatrix.ops._
 import is.hail.types.virtual.{TFloat64, TInt64, TStruct}
 import is.hail.utils._
-
 import breeze.linalg.{*, diag, DenseMatrix => BDM, DenseVector => BDV}
+import is.hail.check.Arbitrary.arbitrary
+import is.hail.check.Gen._
+import is.hail.check.Prop.forAll
+import is.hail.check.{Arbitrary, Gen}
 import org.apache.spark.sql.Row
 import org.testng.annotations.Test
 
diff --git a/hail/hail/test/src/is/hail/methods/ExprSuite.scala b/hail/hail/test/src/is/hail/methods/ExprSuite.scala
index bc16f8b169b..1d8f10befb5 100644
--- a/hail/hail/test/src/is/hail/methods/ExprSuite.scala
+++ b/hail/hail/test/src/is/hail/methods/ExprSuite.scala
@@ -2,7 +2,6 @@ package is.hail.methods
 
 import is.hail.HailSuite
 import is.hail.backend.HailStateManager
-import is.hail.check.Prop._
 import is.hail.check.Properties
 import is.hail.expr._
 import is.hail.expr.ir.IRParser
diff --git a/hail/hail/test/src/is/hail/methods/LocalLDPruneSuite.scala b/hail/hail/test/src/is/hail/methods/LocalLDPruneSuite.scala
index 4be2d10f0bf..63ce2cd71c1 100644
--- a/hail/hail/test/src/is/hail/methods/LocalLDPruneSuite.scala
+++ b/hail/hail/test/src/is/hail/methods/LocalLDPruneSuite.scala
@@ -3,7 +3,6 @@ package is.hail.methods
 import is.hail.{HailSuite, TestUtils}
 import is.hail.annotations.Annotation
 import is.hail.check.{Gen, Properties}
-import is.hail.check.Prop._
 import is.hail.expr.ir.{Interpret, MatrixValue, TableValue}
 import is.hail.utils._
 import is.hail.variant._
diff --git a/hail/hail/test/src/is/hail/types/physical/GenInstances.scala b/hail/hail/test/src/is/hail/types/physical/GenInstances.scala
new file mode 100644
index 00000000000..63399e65c13
--- /dev/null
+++ b/hail/hail/test/src/is/hail/types/physical/GenInstances.scala
@@ -0,0 +1,623 @@
+package is.hail.types.physical
+
+import is.hail.annotations.{Annotation, ExtendedOrdering}
+import is.hail.backend.HailStateManager
+import is.hail.check.Arbitrary.arbitrary
+import is.hail.check.{Arbitrary, Gen}
+import is.hail.types.virtual.{
+  Field, TArray, TBoolean, TCall, TDict, TFloat32, TFloat64, TInt32, TInt64, TInterval, TLocus,
+  TSet, TString, TStruct, TTuple, Type,
+}
+import is.hail.utils.{Interval, genDNAString, triangle, uniqueMaxIndex}
+import is.hail.variant.Call.{
+  alleleByIndex, allelePair, alleles, isPhased, ploidy, unphasedDiploidGtIndex,
+}
+import is.hail.variant.Genotype.gqFromPL
+import is.hail.variant.{AllelePair, Call, Call2, CallN, Locus, ReferenceGenome}
+import org.apache.spark.sql.Row
+
+import scala.annotation.switch
+
+trait GenInstances {
+
+  def genScalar(required: Boolean): Gen[PType] =
+    Gen.oneOf(
+      PBoolean(required),
+      PInt32(required),
+      PInt64(required),
+      PFloat32(required),
+      PFloat64(required),
+      PCanonicalString(required),
+      PCanonicalCall(required),
+    )
+
+  val genOptionalScalar: Gen[PType] = genScalar(false)
+
+  val genRequiredScalar: Gen[PType] = genScalar(true)
+
+  def genComplexType(required: Boolean): Gen[PType] = {
+    val rgDependents = ReferenceGenome.hailReferences.toArray.map(PCanonicalLocus(_, required))
+    val others = Array(PCanonicalCall(required))
+    Gen.oneOfSeq(rgDependents ++ others)
+  }
+
+  def genFields(required: Boolean, genFieldType: Gen[PType]): Gen[Array[PField]] =
+    Gen.buildableOf[Array](
+      Gen.zip(Gen.identifier, genFieldType)
+    )
+      .filter(fields => fields.map(_._1).areDistinct())
+      .map(fields =>
+        fields
+          .iterator
+          .zipWithIndex
+          .map { case ((k, t), i) => PField(k, t, i) }
+          .toArray
+      )
+
+  def preGenStruct(required: Boolean, genFieldType: Gen[PType]): Gen[PStruct] =
+    for (fields <- genFields(required, genFieldType)) yield PCanonicalStruct(fields, required)
+
+  def preGenTuple(required: Boolean, genFieldType: Gen[PType]): Gen[PTuple] =
+    for (fields <- genFields(required, genFieldType))
+      yield PCanonicalTuple(required, fields.map(_.typ): _*)
+
+  private val defaultRequiredGenRatio = 0.2
+
+  def genStruct: Gen[PStruct] = Gen.coin(defaultRequiredGenRatio).flatMap(preGenStruct(_, genArb))
+
+  val genOptionalStruct: Gen[PType] = preGenStruct(required = false, genArb)
+
+  val genRequiredStruct: Gen[PType] = preGenStruct(required = true, genArb)
+
+  val genInsertableStruct: Gen[PStruct] = Gen.coin(defaultRequiredGenRatio).flatMap(required =>
+    if (required)
+      preGenStruct(required = true, genArb)
+    else
+      preGenStruct(required = false, genOptional)
+  )
+
+  def genSized(size: Int, required: Boolean, genPStruct: Gen[PStruct]): Gen[PType] =
+    if (size < 1)
+      Gen.const(PCanonicalStruct.empty(required))
+    else if (size < 2)
+      genScalar(required)
+    else {
+      Gen.frequency(
+        (4, genScalar(required)),
+        (1, genComplexType(required)),
+        (
+          1,
+          genArb.map {
+            PCanonicalArray(_)
+          },
+        ),
+        (
+          1,
+          genArb.map {
+            PCanonicalSet(_)
+          },
+        ),
+        (
+          1,
+          genArb.map {
+            PCanonicalInterval(_)
+          },
+        ),
+        (1, preGenTuple(required, genArb)),
+        (1, Gen.zip(genRequired, genArb).map { case (k, v) => PCanonicalDict(k, v) }),
+        (1, genPStruct.resize(size)),
+      )
+    }
+
+  def preGenArb(required: Boolean, genStruct: Gen[PStruct] = genStruct): Gen[PType] =
+    Gen.sized(genSized(_, required, genStruct))
+
+  def genArb: Gen[PType] = Gen.coin(0.2).flatMap(preGenArb(_))
+
+  val genOptional: Gen[PType] = preGenArb(required = false)
+
+  val genRequired: Gen[PType] = preGenArb(required = true)
+
+  val genInsertable: Gen[PStruct] = genInsertableStruct
+
+  implicit def arbType: Arbitrary[PType] = Arbitrary(genArb)
+
+  implicit val arbPArray: Arbitrary[PArray] =
+    Gen {
+      for {
+        elem <- arbitrary[PType]
+        required <- arbitrary[Boolean]
+      } yield PCanonicalArray(elem, required)
+
+      def genNonmissingValue(sm: HailStateManager): Gen[IndexedSeq[Annotation]] =
+        Gen.buildableOf[Array](elementType.genValue(sm)).map(x => x: IndexedSeq[Annotation])
+    }
+
+  object Contig {
+    def gen(rg: ReferenceGenome): Gen[(String, Int)] = Gen.oneOfSeq(rg.lengths.toSeq)
+  }
+
+  object Locus {
+    def gen(rg: ReferenceGenome): Gen[Locus] =
+      for {
+        (contig, length) <- Contig.gen(rg)
+        pos <- Gen.choose(1, length)
+      } yield Locus(contig, pos)
+  }
+
+  object Call {
+    def check(c: Call, nAlleles: Int): Unit = {
+      (ploidy(c): @switch) match {
+        case 0 =>
+        case 1 =>
+          val a = alleleByIndex(c, 0)
+          assert(a >= 0 && a < nAlleles)
+        case 2 =>
+          val nGenotypes = triangle(nAlleles)
+          val udtn =
+            if (isPhased(c)) {
+              val p = allelePair(c)
+              unphasedDiploidGtIndex(Call2(AllelePair.j(p), AllelePair.k(p)))
+            } else
+              unphasedDiploidGtIndex(c)
+          assert(
+            udtn < nGenotypes,
+            s"Invalid call found '${c.toString}' for number of alleles equal to '$nAlleles'.",
+          )
+        case _ =>
+          alleles(c).foreach(a => assert(a >= 0 && a < nAlleles))
+      }
+    }
+
+    def gen(
+      nAlleles: Int,
+      ploidyGen: Gen[Int] = Gen.choose(0, 2),
+      phasedGen: Gen[Boolean] = Gen.nextCoin(0.5),
+    ): Gen[Call] = for {
+      ploidy <- ploidyGen
+      phased <- phasedGen
+      alleles <- Gen.buildableOfN[Array](ploidy, Gen.choose(0, nAlleles - 1))
+    } yield {
+      val c = CallN(alleles, phased)
+      check(c, nAlleles)
+      c
+    }
+
+    def genUnphasedDiploid(nAlleles: Int): Gen[Call] = gen(nAlleles, Gen.const(2), Gen.const(false))
+
+    def genPhasedDiploid(nAlleles: Int): Gen[Call] = gen(nAlleles, Gen.const(2), Gen.const(true))
+
+    def genNonmissingValue: Gen[Call] = for {
+      nAlleles <- Gen.choose(2, 5)
+      c <- gen(nAlleles)
+    } yield {
+      check(c, nAlleles)
+      c
+    }
+  }
+
+  object Genotype {
+    def genExtremeNonmissing(nAlleles: Int): Gen[Annotation] = {
+      val m = Int.MaxValue / (nAlleles + 1)
+      val nGenotypes = triangle(nAlleles)
+      val gg = for {
+        c: Option[Call] <- Gen.option(Call.genUnphasedDiploid(nAlleles))
+        ad <- Gen.option(Gen.buildableOfN[Array](nAlleles, Gen.choose(0, m)))
+        dp <- Gen.option(Gen.choose(0, m))
+        gq <- Gen.option(Gen.choose(0, 10000))
+        pl <- Gen.oneOfGen(
+          Gen.option(Gen.buildableOfN[Array](nGenotypes, Gen.choose(0, m))),
+          Gen.option(Gen.buildableOfN[Array](nGenotypes, Gen.choose(0, 100))),
+        )
+      } yield {
+        c.foreach(c => pl.foreach(pla => pla(Call.unphasedDiploidGtIndex(c)) = 0))
+        pl.foreach { pla =>
+          val m = pla.min
+          var i = 0
+          while (i < pla.length) {
+            pla(i) -= m
+            i += 1
+          }
+        }
+        val g = Annotation(
+          c.orNull,
+          ad.map(a => a: IndexedSeq[Int]).orNull,
+          dp.map(_ + ad.map(_.sum).getOrElse(0)).orNull,
+          gq.orNull,
+          pl.map(a => a: IndexedSeq[Int]).orNull,
+        )
+        g
+      }
+      gg
+    }
+
+    def genExtreme(nAlleles: Int): Gen[Annotation] =
+      Gen.frequency(
+        (100, genExtremeNonmissing(nAlleles)),
+        (1, Gen.const(null)),
+      )
+
+    def genRealisticNonmissing(nAlleles: Int): Gen[Annotation] = {
+      val nGenotypes = triangle(nAlleles)
+      val gg = for {
+        callRate <- Gen.choose(0d, 1d)
+        alleleFrequencies <-
+          Gen.buildableOfN[Array](nAlleles, Gen.choose(1e-6, 1d)) // avoid divison by 0
+            .map { rawWeights =>
+              val sum = rawWeights.sum
+              rawWeights.map(_ / sum)
+            }
+        c <- Gen.option(
+          Gen.zip(
+            Gen.chooseWithWeights(alleleFrequencies),
+            Gen.chooseWithWeights(alleleFrequencies),
+          )
+            .map { case (gti, gtj) => Call2(gti, gtj) },
+          callRate,
+        )
+        ad <- Gen.option(Gen.buildableOfN[Array](nAlleles, Gen.choose(0, 50)))
+        dp <- Gen.choose(0, 30).map(d => ad.map(o => o.sum + d))
+        pl <- Gen.option(Gen.buildableOfN[Array](nGenotypes, Gen.choose(0, 1000)).map { arr =>
+          c match {
+            case Some(x) =>
+              arr(Call.unphasedDiploidGtIndex(x)) = 0
+              arr
+            case None =>
+              val min = arr.min
+              arr.map(_ - min)
+          }
+        })
+        gq <- Gen.choose(-30, 30).map(i => pl.map(pls => math.max(0, gqFromPL(pls) + i)))
+      } yield Annotation(c.orNull, ad.map(a => a: IndexedSeq[Int]).orNull, dp.orNull, gq.orNull, pl.map(a => a: IndexedSeq[Int]).orNull)
+      gg
+    }
+
+    def genRealistic(nAlleles: Int): Gen[Annotation] =
+      Gen.frequency(
+        (100, genRealisticNonmissing(nAlleles)),
+        (1, Gen.const(null)),
+      )
+
+    def genGenericCallAndProbabilitiesGenotype(nAlleles: Int): Gen[Annotation] = {
+      val nGenotypes = triangle(nAlleles)
+      val gg = for (gp <- Gen.option(Gen.partition(nGenotypes, 32768))) yield {
+        val c = gp.flatMap(a => Option(uniqueMaxIndex(a))).map(Call2.fromUnphasedDiploidGtIndex(_))
+        Row(
+          c.orNull,
+          gp.map(gpx => gpx.map(p => p.toDouble / 32768): IndexedSeq[Double]).orNull,
+        )
+      }
+      Gen.frequency(
+        (100, gg),
+        (1, Gen.const(null)),
+      )
+    }
+  }
+
+  object VariantSubgen {
+    def random(rg: ReferenceGenome): VariantSubgen = VariantSubgen(
+      contigGen = Contig.gen(rg),
+      nAllelesGen = Gen.frequency((5, Gen.const(2)), (1, Gen.choose(2, 10))),
+      refGen = genDNAString,
+      altGen = Gen.frequency((10, genDNAString), (1, Gen.const("*"))),
+    )
+
+    def plinkCompatible(rg: ReferenceGenome): VariantSubgen = {
+      val r = random(rg)
+      val compatible = (1 until 22).map(_.toString).toSet
+      r.copy(
+        contigGen = r.contigGen.filter { case (contig, _) =>
+          compatible.contains(contig)
+        }
+      )
+    }
+
+    def biallelic(rg: ReferenceGenome): VariantSubgen = random(rg).copy(nAllelesGen = Gen.const(2))
+
+    def plinkCompatibleBiallelic(rg: ReferenceGenome): VariantSubgen =
+      plinkCompatible(rg).copy(nAllelesGen = Gen.const(2))
+  }
+
+  case class VariantSubgen(
+    contigGen: Gen[(String, Int)],
+    nAllelesGen: Gen[Int],
+    refGen: Gen[String],
+    altGen: Gen[String],
+  ) {
+
+    def genLocusAlleles: Gen[Annotation] =
+      for {
+        (contig, length) <- contigGen
+        start <- Gen.choose(1, length)
+        nAlleles <- nAllelesGen
+        ref <- refGen
+        altAlleles <- Gen.distinctBuildableOfN[Array](
+          nAlleles - 1,
+          altGen,
+        )
+          .filter(!_.contains(ref))
+      } yield Annotation(Locus(contig, start), (ref +: altAlleles).toFastSeq)
+  }
+
+  object ReferenceGenome {
+    def gen: Gen[ReferenceGenome] =
+      for {
+        name <- Gen.identifier.filter(!ReferenceGenome.hailReferences.contains(_))
+        nContigs <- Gen.choose(3, 10)
+        contigs <- Gen.distinctBuildableOfN[Array](nContigs, Gen.identifier)
+        lengths <- Gen.buildableOfN[Array](nContigs, Gen.choose(1000000, 500000000))
+        contigsIndex = contigs.zip(lengths).toMap
+        xContig <- Gen.oneOfSeq(contigs)
+        parXA <- Gen.choose(0, contigsIndex(xContig))
+        parXB <- Gen.choose(0, contigsIndex(xContig))
+        yContig <- Gen.oneOfSeq(contigs) if yContig != xContig
+        parYA <- Gen.choose(0, contigsIndex(yContig))
+        parYB <- Gen.choose(0, contigsIndex(yContig))
+        mtContig <- Gen.oneOfSeq(contigs) if mtContig != xContig && mtContig != yContig
+      } yield ReferenceGenome(
+        name,
+        contigs,
+        contigs.zip(lengths).toMap,
+        Set(xContig),
+        Set(yContig),
+        Set(mtContig),
+        Array(
+          (Locus(xContig, math.min(parXA, parXB)), Locus(xContig, math.max(parXA, parXB))),
+          (Locus(yContig, math.min(parYA, parYB)), Locus(yContig, math.max(parYA, parYB))),
+        ),
+      )
+  }
+
+  object Type {
+    def genScalar(): Gen[Type] =
+      Gen.oneOf(TBoolean, TInt32, TInt64, TFloat32,
+        TFloat64, TString, TCall)
+
+    def genComplexType(): Gen[Type] = {
+      val rgDependents = ReferenceGenome.hailReferences.toArray.map(TLocus(_))
+      val others = Array(TCall)
+      Gen.oneOfSeq(rgDependents ++ others)
+    }
+
+    def genFields(genFieldType: Gen[Type]): Gen[Array[Field]] = {
+      Gen.buildableOf[Array](
+        Gen.zip(Gen.identifier, genFieldType)
+      )
+        .filter(fields => fields.map(_._1).areDistinct())
+        .map(fields =>
+          fields
+            .iterator
+            .zipWithIndex
+            .map { case ((k, t), i) => Field(k, t, i) }
+            .toArray
+        )
+    }
+
+    def preGenStruct(genFieldType: Gen[Type]): Gen[TStruct] =
+      for (fields <- genFields(genFieldType)) yield TStruct(fields)
+
+    def preGenTuple(genFieldType: Gen[Type]): Gen[TTuple] =
+      for (fields <- genFields(genFieldType)) yield TTuple(fields.map(_.typ): _*)
+
+    private val defaultRequiredGenRatio = 0.2
+
+    def genStruct: Gen[TStruct] =
+      Gen.coin(defaultRequiredGenRatio).flatMap(c => preGenStruct(genArb))
+
+    def genSized(size: Int, genTStruct: Gen[TStruct]): Gen[Type] =
+      if (size < 1)
+        Gen.const(TStruct.empty)
+      else if (size < 2)
+        genScalar()
+      else {
+        Gen.frequency(
+          (4, genScalar()),
+          (1, genComplexType()),
+          (
+            1,
+            genArb.map {
+              TArray(_)
+            },
+          ),
+          (
+            1,
+            genArb.map {
+              TSet(_)
+            },
+          ),
+          (
+            1,
+            genArb.map {
+              TInterval(_)
+            },
+          ),
+          (1, preGenTuple(genArb)),
+          (1, Gen.zip(genRequired, genArb).map { case (k, v) => TDict(k, v) }),
+          (1, genTStruct.resize(size)),
+        )
+      }
+
+    def preGenArb(genStruct: Gen[TStruct] = genStruct): Gen[Type] =
+      Gen.sized(genSized(_, genStruct))
+
+    def genArb: Gen[Type] = preGenArb()
+
+    val genOptional: Gen[Type] = preGenArb()
+
+    val genRequired: Gen[Type] = preGenArb()
+
+    def genWithValue(sm: HailStateManager): Gen[(Type, Annotation)] = for {
+      s <- Gen.size
+      // prefer smaller type and bigger values
+      fraction <- Gen.choose(0.1, 0.3)
+      x = (fraction * s).toInt
+      y = s - x
+      t <- Type.genStruct.resize(x)
+      v <- t.genValue(sm).resize(y)
+    } yield (t, v)
+
+    implicit def arbType: Arbitrary[Type] =
+      Arbitrary(genArb)
+  }
+
+  object PBaseStruct {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      if (types.isEmpty) {
+        Gen.const(Annotation.empty)
+      } else
+        Gen.uniformSequence(types.map(t => t.genValue(sm))).map(a => Annotation(a: _*))
+  }
+
+  object PDict {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      Gen.buildableOf2[Map](Gen.zip(keyType.genValue(sm), valueType.genValue(sm)))
+  }
+
+  object PSet {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      Gen.buildableOf[Set](elementType.genValue(sm))
+  }
+
+  object TInterval {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      Interval.gen(pointType.ordering(sm), pointType.genValue(sm))
+  }
+
+  trait Type {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation]
+
+    def genValue(sm: HailStateManager): Gen[Annotation] =
+      Gen.nextCoin(0.05).flatMap(isEmpty =>
+        if (isEmpty) Gen.const(null) else genNonmissingValue(sm)
+      )
+  }
+
+  trait TRNGState {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
+  }
+
+  trait TUnion {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
+  }
+
+  trait TVariable {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
+  }
+
+  trait TVoid {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
+  }
+
+  trait TArray {
+    def genNonmissingValue(sm: HailStateManager): Gen[IndexedSeq[Annotation]] =
+      Gen.buildableOf[Array](elementType.genValue(sm)).map(x => x: IndexedSeq[Annotation])
+  }
+
+  trait TBaseStruct {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      if (types.isEmpty) {
+        Gen.const(Annotation.empty)
+      } else
+        Gen.size.flatMap(fuel =>
+          if (types.length > fuel)
+            Gen.uniformSequence(types.map(t => Gen.const(null))).map(a => Annotation(a: _*))
+          else
+            Gen.uniformSequence(types.map(t => t.genValue(sm))).map(a => Annotation(a: _*))
+        )
+  }
+
+  trait TBinary {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      Gen.buildableOf(arbitrary[Byte])
+  }
+
+  trait TBoolean {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      arbitrary[Boolean]
+  }
+
+  trait TCall {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      Call.genNonmissingValue
+  }
+
+  trait Foo {
+    def genValue(sm: HailStateManager): Gen[Annotation] =
+      if (required) genNonmissingValue(sm)
+      else Gen.nextCoin(0.05).flatMap(isEmpty =>
+        if (isEmpty) Gen.const(null) else genNonmissingValue(sm)
+      )
+
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      virtualType.genNonmissingValue(sm)
+  }
+
+  trait TDict {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      Gen.buildableOf2[Map](Gen.zip(keyType.genValue(sm), valueType.genValue(sm)))
+  }
+
+  trait TFloat32 {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      arbitrary[Float]
+  }
+
+  trait TFloat64 {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      arbitrary[Double]
+  }
+
+  trait TInt32 {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      arbitrary[Int]
+  }
+
+  trait TInt64 {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      arbitrary[Long]
+  }
+
+  trait TLocus {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      Locus.gen(sm.referenceGenomes(rgName))
+  }
+
+  trait TNDArray {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = ???
+  }
+
+  trait TSet {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      Gen.buildableOf[Set](elementType.genValue(sm))
+  }
+
+  trait TStream {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] =
+      throw new UnsupportedOperationException("Streams don't have associated annotations.")
+  }
+
+  trait TString {
+    def genNonmissingValue(sm: HailStateManager): Gen[Annotation] = arbitrary[String]
+  }
+
+  trait Interval {
+    def gen[P](pord: ExtendedOrdering, pgen: Gen[P]): Gen[Interval] =
+      Gen.zip(pgen, pgen, Gen.coin(), Gen.coin())
+        .filter { case (x, y, s, e) => pord.compare(x, y) != 0 || (s && e) }
+        .map { case (x, y, s, e) =>
+          if (pord.compare(x, y) < 0)
+            Interval(x, y, s, e)
+          else
+            Interval(y, x, s, e)
+        }
+  }
+
+  object utils {
+    def genBase: Gen[Char] = Gen.oneOf('A', 'C', 'T', 'G')
+
+    def genDNAString: Gen[String] = Gen.stringOf(genBase)
+      .resize(12)
+      .filter(s => !s.isEmpty)
+  }
+
+}
diff --git a/hail/hail/test/src/is/hail/utils/BinaryHeapSuite.scala b/hail/hail/test/src/is/hail/utils/BinaryHeapSuite.scala
index ea1f69313d8..ccb0796ce5d 100644
--- a/hail/hail/test/src/is/hail/utils/BinaryHeapSuite.scala
+++ b/hail/hail/test/src/is/hail/utils/BinaryHeapSuite.scala
@@ -1,8 +1,6 @@
 package is.hail.utils
 
-import is.hail.check.Arbitrary._
 import is.hail.check.Gen
-import is.hail.check.Prop._
 
 import scala.collection.mutable
 
diff --git a/hail/hail/test/src/is/hail/utils/BitVectorSuite.scala b/hail/hail/test/src/is/hail/utils/BitVectorSuite.scala
index af287922264..d6902df2fcb 100644
--- a/hail/hail/test/src/is/hail/utils/BitVectorSuite.scala
+++ b/hail/hail/test/src/is/hail/utils/BitVectorSuite.scala
@@ -1,8 +1,5 @@
 package is.hail.utils
 
-import is.hail.check._
-import is.hail.check.Prop._
-
 import org.scalatestplus.testng.TestNGSuite
 import org.testng.annotations.Test
 
diff --git a/hail/hail/test/src/is/hail/variant/GenotypeSuite.scala b/hail/hail/test/src/is/hail/variant/GenotypeSuite.scala
index f88eff4b872..a2a057b30fc 100644
--- a/hail/hail/test/src/is/hail/variant/GenotypeSuite.scala
+++ b/hail/hail/test/src/is/hail/variant/GenotypeSuite.scala
@@ -2,7 +2,6 @@ package is.hail.variant
 
 import is.hail.TestUtils
 import is.hail.check.Gen
-import is.hail.check.Prop._
 import is.hail.testUtils.Variant
 import is.hail.utils._
 
diff --git a/hail/hail/test/src/is/hail/variant/ReferenceGenomeSuite.scala b/hail/hail/test/src/is/hail/variant/ReferenceGenomeSuite.scala
index 693a56c6061..05422e43c51 100644
--- a/hail/hail/test/src/is/hail/variant/ReferenceGenomeSuite.scala
+++ b/hail/hail/test/src/is/hail/variant/ReferenceGenomeSuite.scala
@@ -2,7 +2,6 @@ package is.hail.variant
 
 import is.hail.{HailSuite, TestUtils}
 import is.hail.backend.{ExecuteContext, HailStateManager}
-import is.hail.check.Prop._
 import is.hail.check.Properties
 import is.hail.expr.ir.EmitFunctionBuilder
 import is.hail.io.reference.{FASTAReader, FASTAReaderConfig, LiftOver}