Updte test expectations for changing column type

Previously, we tested that changing a column type preserved the default
and check constraints on the column. We now want to reverse this
decision and test that they are *not* preserved.

pkg/migrations/op_change_type_test.go

@@ -225,7 +225,7 @@ func TestChangeColumnType(t *testing.T) {
 			},
 		},
 		{
-			name: "changing column type preserves any defaults on the column",
+			name: "changing column type removes any default on the column",
 			migrations: []migrations.Migration{
 				{
 					Name: "01_add_table",
@@ -239,9 +239,9 @@ func TestChangeColumnType(t *testing.T) {
 									Pk:   ptr(true),
 								},
 								{
-									Name:     "username",
+									Name:     "age",
 									Type:     "text",
-									Default:  ptr("'alice'"),
+									Default:  ptr("'0'"),
 									Nullable: ptr(true),
 								},
 							},
@@ -253,10 +253,10 @@ func TestChangeColumnType(t *testing.T) {
 					Operations: migrations.Operations{
 						&migrations.OpAlterColumn{
 							Table:  "users",
-							Column: "username",
-							Type:   ptr("varchar(255)"),
-							Up:     "username",
-							Down:   "username",
+							Column: "age",
+							Type:   ptr("integer"),
+							Up:     "CAST(age AS integer)",
+							Down:   "CAST(age AS text)",
 						},
 					},
 				},
@@ -267,10 +267,10 @@ func TestChangeColumnType(t *testing.T) {
 					"id": "1",
 				})
 
-				// The newly inserted row respects the default value of the column.
+				// The newly inserted row contains a NULL instead of the old default value.
 				rows := MustSelect(t, db, schema, "02_change_type", "users")
 				assert.Equal(t, []map[string]any{
-					{"id": 1, "username": "alice"},
+					{"id": 1, "age": nil},
 				}, rows)
 			},
 			afterRollback: func(t *testing.T, db *sql.DB, schema string) {
@@ -281,16 +281,16 @@ func TestChangeColumnType(t *testing.T) {
 					"id": "2",
 				})
 
-				// The newly inserted row respects the default value of the column.
+				// The newly inserted row contains a NULL instead of the old default value.
 				rows := MustSelect(t, db, schema, "02_change_type", "users")
 				assert.Equal(t, []map[string]any{
-					{"id": 1, "username": "alice"},
-					{"id": 2, "username": "alice"},
+					{"id": 1, "age": nil},
+					{"id": 2, "age": nil},
 				}, rows)
 			},
 		},
 		{
-			name: "changing column type preserves any check constraints on the column",
+			name: "changing column type removes any check constraints on the column",
 			migrations: []migrations.Migration{
 				{
 					Name: "01_add_table",
@@ -304,12 +304,12 @@ func TestChangeColumnType(t *testing.T) {
 									Pk:   ptr(true),
 								},
 								{
-									Name:     "username",
+									Name:     "age",
 									Type:     "text",
 									Nullable: ptr(true),
 									Check: &migrations.CheckConstraint{
-										Name:       "username_length",
-										Constraint: "length(username) > 3",
+										Name:       "age_length",
+										Constraint: "length(age) < 3",
 									},
 								},
 							},
@@ -321,29 +321,31 @@ func TestChangeColumnType(t *testing.T) {
 					Operations: migrations.Operations{
 						&migrations.OpAlterColumn{
 							Table:  "users",
-							Column: "username",
-							Type:   ptr("varchar(255)"),
-							Up:     "username",
-							Down:   "username",
+							Column: "age",
+							Type:   ptr("integer"),
+							Up:     "CAST(age AS integer)",
+							Down:   "(SELECT CASE WHEN age < 100 THEN age::text ELSE '0' END)",
 						},
 					},
 				},
 			},
 			afterStart: func(t *testing.T, db *sql.DB, schema string) {
-				// Inserting a row that violates the check constraint should fail.
-				MustNotInsert(t, db, schema, "02_change_type", "users", map[string]string{
-					"id":       "1",
-					"username": "a",
-				}, testutils.CheckViolationErrorCode)
+				// Inserting a row into the new schema that violates the check
+				// constraint on the old schema should succeed.
+				MustInsert(t, db, schema, "02_change_type", "users", map[string]string{
+					"id":  "1",
+					"age": "1111",
+				})
 			},
 			afterRollback: func(t *testing.T, db *sql.DB, schema string) {
 			},
 			afterComplete: func(t *testing.T, db *sql.DB, schema string) {
-				// Inserting a row that violates the check constraint should fail.
-				MustNotInsert(t, db, schema, "02_change_type", "users", map[string]string{
-					"id":       "2",
-					"username": "b",
-				}, testutils.CheckViolationErrorCode)
+				// Inserting a row into the new schema that violates the check
+				// constraint on the old schema should succeed.
+				MustInsert(t, db, schema, "02_change_type", "users", map[string]string{
+					"id":  "2",
+					"age": "2222",
+				})
 			},
 		},
 		{