feat: Add destination tests for removing a unique constraint (#1558)

#### Summary

This adds a test for how destinations will handle removing a unique constraint

Author: bbernays

plugin/testing_write.go

@@ -39,12 +39,13 @@ type WriterTestSuite struct {
 
 // SafeMigrations defines which migrations are supported by the plugin in safe migrate mode
 type SafeMigrations struct {
-	AddColumn           bool
-	AddColumnNotNull    bool
-	RemoveColumn        bool
-	RemoveColumnNotNull bool
-	ChangeColumn        bool
-	MovePKToCQOnly      bool
+	AddColumn              bool
+	AddColumnNotNull       bool
+	RemoveColumn           bool
+	RemoveColumnNotNull    bool
+	ChangeColumn           bool
+	RemoveUniqueConstraint bool
+	MovePKToCQOnly         bool
 }
 
 type WriterTestSuiteTests struct {

plugin/testing_write_migrate.go

@@ -249,6 +249,33 @@ func (s *WriterTestSuite) testMigrate(
 		}
 	})
 
+	t.Run("remove_unique_constraint_only"+suffix, func(t *testing.T) {
+		if !forceMigrate && !s.tests.SafeMigrations.RemoveUniqueConstraint {
+			t.Skip("skipping test: remove_unique_constraint_only")
+		}
+		tableName := "remove_unique_constraint_only" + suffix + "_" + tableUUIDSuffix()
+		source := &schema.Table{
+			Name: tableName,
+			Columns: schema.ColumnList{
+				{Name: "_cq_id", Type: types.ExtensionTypes.UUID, Unique: true},
+				{Name: "id", Type: arrow.PrimitiveTypes.Int64},
+				{Name: "uuid", Type: types.ExtensionTypes.UUID},
+				{Name: "bool", Type: arrow.FixedWidthTypes.Boolean, NotNull: true},
+			}}
+		target := &schema.Table{
+			Name: tableName,
+			Columns: schema.ColumnList{
+				{Name: "_cq_id", Type: types.ExtensionTypes.UUID},
+				{Name: "id", Type: arrow.PrimitiveTypes.Int64},
+				{Name: "uuid", Type: types.ExtensionTypes.UUID},
+				{Name: "bool", Type: arrow.FixedWidthTypes.Boolean, NotNull: true},
+			}}
+		require.NoError(t, s.migrate(ctx, target, source, s.tests.SafeMigrations.RemoveUniqueConstraint, forceMigrate))
+		if !forceMigrate {
+			require.NoError(t, s.migrate(ctx, target, target, true, false))
+		}
+	})
+
 	t.Run("move_to_cq_id_only"+suffix, func(t *testing.T) {
 		if !forceMigrate && !s.tests.SafeMigrations.MovePKToCQOnly {
 			t.Skip("skipping test: move_to_cq_id_only")