Switch to ginkgo/gomega for tests

This switches over to ginkgo/gomega for tests, which makes writing
certain tests easier/more fluent in the future.

vendor/github.com/onsi/gomega/matchers/have_occurred_matcher.go

@@ -0,0 +1,33 @@
+package matchers
+
+import (
+	"fmt"
+
+	"github.com/onsi/gomega/format"
+)
+
+type HaveOccurredMatcher struct {
+}
+
+func (matcher *HaveOccurredMatcher) Match(actual interface{}) (success bool, err error) {
+	// is purely nil?
+	if actual == nil {
+		return false, nil
+	}
+
+	// must be an 'error' type
+	if !isError(actual) {
+		return false, fmt.Errorf("Expected an error-type.  Got:\n%s", format.Object(actual, 1))
+	}
+
+	// must be non-nil (or a pointer to a non-nil)
+	return !isNil(actual), nil
+}
+
+func (matcher *HaveOccurredMatcher) FailureMessage(actual interface{}) (message string) {
+	return fmt.Sprintf("Expected an error to have occurred.  Got:\n%s", format.Object(actual, 1))
+}
+
+func (matcher *HaveOccurredMatcher) NegatedFailureMessage(actual interface{}) (message string) {
+	return fmt.Sprintf("Expected error:\n%s\n%s\n%s", format.Object(actual, 1), format.IndentString(actual.(error).Error(), 1), "not to have occurred")
+}