Improving the ToUnit test coverage (#1493)

Improving the `ToUnit` test coverage:
- `ToUnit_FromNonBaseUnit_ReturnsQuantityWithGivenUnit` now also tests
the non-base to non-base conversions
- `ToUnit_FromNonBaseUnit_ReturnsQuantityWithGivenUnit` is no longer
skipped for quantities with a single unit (the test is still generated)
- added the `ToUnit_FromIQuantity_ReturnsTheExpectedIQuantity` test:
covering the `IQuantity` interfaces
- added the `Convert_GetTypeCode_Returns_Object` test (completing the
`IConvertible` interface coverage)
- `IQuantityTests`: removed the redundant `UnitSystem` tests and updated
"wrong unit type" tests, using all quantities

CodeGen/Generators/UnitsNetGen/UnitTestBaseClassGenerator.cs

@@ -797,16 +797,16 @@ public void ToUnit_WithSameUnits_AreEqual({_unitEnumName} unit)
             Assert.Equal(quantity, toUnitWithSameUnit);
         }}
 
-        [Theory{(_quantity.Units.Length == 1 ? "(Skip = \"Multiple units required\")" : string.Empty)}]
+        [Theory]
         [MemberData(nameof(UnitTypes))]
         public void ToUnit_FromNonBaseUnit_ReturnsQuantityWithGivenUnit({_unitEnumName} unit)
         {{
-            // See if there is a unit available that is not the base unit, fallback to base unit if it has only a single unit.
-            var fromUnit = {_quantity.Name}.Units.First(u => u != {_quantity.Name}.BaseUnit);
-
-            var quantity = {_quantity.Name}.From(3.0, fromUnit);
-            var converted = quantity.ToUnit(unit);
-            Assert.Equal(converted.Unit, unit);
+            Assert.All({_quantity.Name}.Units.Where(u => u != {_quantity.Name}.BaseUnit), fromUnit =>
+            {{
+                var quantity = {_quantity.Name}.From(3.0, fromUnit);
+                var converted = quantity.ToUnit(unit);
+                Assert.Equal(converted.Unit, unit);
+            }});
         }}
 
         [Theory]
@@ -818,6 +818,25 @@ public virtual void ToUnit_FromDefaultQuantity_ReturnsQuantityWithGivenUnit({_un
             Assert.Equal(converted.Unit, unit);
         }}
 
+        [Theory]
+        [MemberData(nameof(UnitTypes))]
+        public void ToUnit_FromIQuantity_ReturnsTheExpectedIQuantity({_unitEnumName} unit)
+        {{
+            var quantity = {_quantity.Name}.From(3, {_quantity.Name}.BaseUnit);
+            {_quantity.Name} expectedQuantity = quantity.ToUnit(unit);
+            Assert.Multiple(() =>
+            {{
+                IQuantity<{_unitEnumName}> quantityToConvert = quantity;
+                IQuantity<{_unitEnumName}> convertedQuantity = quantityToConvert.ToUnit(unit);
+                Assert.Equal(unit, convertedQuantity.Unit);
+            }}, () =>
+            {{
+                IQuantity quantityToConvert = quantity;
+                IQuantity convertedQuantity = quantityToConvert.ToUnit(unit);
+                Assert.Equal(unit, convertedQuantity.Unit);
+            }});
+        }}
+
         [Fact]
         public void ConversionRoundTrip()
         {{
@@ -1213,6 +1232,13 @@ public void Convert_ChangeType_InvalidType_ThrowsInvalidCastException()
             Assert.Throws<InvalidCastException>(() => Convert.ChangeType(quantity, typeof(QuantityFormatter)));
         }}
 
+        [Fact]
+        public void Convert_GetTypeCode_Returns_Object()
+        {{
+            var quantity = {_quantity.Name}.From{_baseUnit.PluralName}(1.0);
+            Assert.Equal(TypeCode.Object, Convert.GetTypeCode(quantity));
+        }}
+
         [Fact]
         public void GetHashCode_Equals()
         {{

UnitsNet.Tests/CustomCode/IQuantityTests.cs

@@ -2,8 +2,7 @@
 // Copyright 2013 Andreas Gullberg Larsen ([email protected]). Maintained at https://github.com/angularsen/UnitsNet.
 
 using System;
-using System.Diagnostics.CodeAnalysis;
-using UnitsNet.Units;
+using System.Linq;
 using Xunit;
 
 namespace UnitsNet.Tests
@@ -14,48 +13,19 @@ public partial class IQuantityTests
         [Fact]
         public void As_GivenWrongUnitType_ThrowsArgumentException()
         {
-            IQuantity length = Length.FromMeters(1.2345);
-            Assert.Throws<ArgumentException>(() => length.As(MassUnit.Kilogram));
-        }
-
-        [Fact]
-        [SuppressMessage("ReSharper", "AssignNullToNotNullAttribute")]
-        public void As_GivenNullUnitSystem_ThrowsArgumentNullException()
-        {
-            IQuantity imperialLengthQuantity = new Length(2.0, LengthUnit.Inch);
-            Assert.Throws<ArgumentNullException>(() => imperialLengthQuantity.As((UnitSystem)null!));
-        }
-
-        [Fact]
-        public void As_GivenSIUnitSystem_ReturnsSIValue()
-        {
-            IQuantity inches = new Length(2.0, LengthUnit.Inch);
-            Assert.Equal(0.0508, inches.As(UnitSystem.SI));
+            Assert.All(Quantity.Infos.Select(x => x.Zero), quantity =>
+            {
+                Assert.Throws<ArgumentException>(() => quantity.As(ComparisonType.Absolute));
+            });
         }
 
         [Fact]
         public void ToUnit_GivenWrongUnitType_ThrowsArgumentException()
         {
-            IQuantity length = Length.FromMeters(1.2345);
-            Assert.Throws<ArgumentException>(() => length.ToUnit(MassUnit.Kilogram));
-        }
-
-        [Fact]
-        public void ToUnit_GivenNullUnitSystem_ThrowsArgumentNullException()
-        {
-            IQuantity imperialLengthQuantity = new Length(2.0, LengthUnit.Inch);
-            Assert.Throws<ArgumentNullException>(() => imperialLengthQuantity.ToUnit((UnitSystem)null!));
-        }
-
-        [Fact]
-        public void ToUnit_GivenSIUnitSystem_ReturnsSIQuantity()
-        {
-            IQuantity inches = new Length(2.0, LengthUnit.Inch);
-
-            IQuantity inSI = inches.ToUnit(UnitSystem.SI);
-
-            Assert.Equal(0.0508, inSI.Value);
-            Assert.Equal(LengthUnit.Meter, inSI.Unit);
+            Assert.All(Quantity.Infos.Select(x => x.Zero), quantity =>
+            {
+                Assert.Throws<ArgumentException>(() => quantity.ToUnit(ComparisonType.Absolute));
+            });
         }
     }
 }