Move version validation tests into separate package

This commit cleans up tests in pkg/apis/version by moving them
into a separate package. This encourages black-box testing.
No functional changes.

pkg/apis/version/version_validation_test.go

@@ -14,13 +14,14 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package version
+package version_test
 
 import (
 	"context"
 	"testing"
 
 	"github.com/tektoncd/pipeline/pkg/apis/config"
+	"github.com/tektoncd/pipeline/pkg/apis/version"
 )
 
 func TestValidateEnabledAPIFields(t *testing.T) {
@@ -35,7 +36,7 @@ func TestValidateEnabledAPIFields(t *testing.T) {
 		FeatureFlags: flags,
 	}
 	ctx := config.ToContext(context.Background(), cfg)
-	if err := ValidateEnabledAPIFields(ctx, "test feature", version); err != nil {
+	if err := version.ValidateEnabledAPIFields(ctx, "test feature", version); err != nil {
 		t.Errorf("unexpected error for compatible feature gates: %q", err)
 	}
 }
@@ -51,7 +52,7 @@ func TestValidateEnabledAPIFieldsError(t *testing.T) {
 		FeatureFlags: flags,
 	}
 	ctx := config.ToContext(context.Background(), cfg)
-	err = ValidateEnabledAPIFields(ctx, "test feature", "alpha")
+	err = version.ValidateEnabledAPIFields(ctx, "test feature", "alpha")
 
 	if err == nil {
 		t.Errorf("error expected for incompatible feature gates")