Fix error messages; add tests

pkg/api/helpers.go

@@ -17,12 +17,29 @@ limitations under the License.
 package api
 
 import (
+	"reflect"
 	"strings"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/resource"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/conversion"
+
+	"github.com/davecgh/go-spew/spew"
 )
 
+// Conversion error conveniently packages up errors in conversions.
+type ConversionError struct {
+	In, Out interface{}
+	Message string
+}
+
+// Return a helpful string about the error
+func (c *ConversionError) Error() string {
+	return spew.Sprintf(
+		"Conversion error: %s. (in: %v(%+v) out: %v)",
+		c.Message, reflect.TypeOf(c.In), c.In, reflect.TypeOf(c.Out),
+	)
+}
+
 // Semantic can do semantic deep equality checks for api objects.
 // Example: api.Semantic.DeepEqual(aPod, aPodWithNonNilButEmptyMaps) == true
 var Semantic = conversion.EqualitiesOrDie(
@@ -38,8 +55,12 @@ var Semantic = conversion.EqualitiesOrDie(
 		if b.Amount == nil && a.MilliValue() == 0 {
 			return true
 		}
+		if a.Amount == nil || b.Amount == nil {
+			return false
+		}
 		return a.Amount.Cmp(b.Amount) == 0
 	},
+	pullPoliciesEqual,
 )
 
 // TODO: Address these per #1502