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/panic_matcher.go

@@ -0,0 +1,46 @@
+package matchers
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/onsi/gomega/format"
+)
+
+type PanicMatcher struct {
+	object interface{}
+}
+
+func (matcher *PanicMatcher) Match(actual interface{}) (success bool, err error) {
+	if actual == nil {
+		return false, fmt.Errorf("PanicMatcher expects a non-nil actual.")
+	}
+
+	actualType := reflect.TypeOf(actual)
+	if actualType.Kind() != reflect.Func {
+		return false, fmt.Errorf("PanicMatcher expects a function.  Got:\n%s", format.Object(actual, 1))
+	}
+	if !(actualType.NumIn() == 0 && actualType.NumOut() == 0) {
+		return false, fmt.Errorf("PanicMatcher expects a function with no arguments and no return value.  Got:\n%s", format.Object(actual, 1))
+	}
+
+	success = false
+	defer func() {
+		if e := recover(); e != nil {
+			matcher.object = e
+			success = true
+		}
+	}()
+
+	reflect.ValueOf(actual).Call([]reflect.Value{})
+
+	return
+}
+
+func (matcher *PanicMatcher) FailureMessage(actual interface{}) (message string) {
+	return format.Message(actual, "to panic")
+}
+
+func (matcher *PanicMatcher) NegatedFailureMessage(actual interface{}) (message string) {
+	return format.Message(actual, fmt.Sprintf("not to panic, but panicked with\n%s", format.Object(matcher.object, 1)))
+}