Add some tests for bundlefile and improve the error messages for LoadFile

Signed-off-by: Daniel Nephin <dnephin@docker.com>

testutil/assert/assert.go

@@ -0,0 +1,47 @@
+// Package assert contains functions for making assertions in unit tests
+package assert
+
+import (
+	"strings"
+)
+
+// TestingT is an interface which defines the methods of testing.T that are
+// required by this package
+type TestingT interface {
+	Fatalf(string, ...interface{})
+}
+
+// Equal compare the actual value to the expected value and fails the test if
+// they are not equal.
+func Equal(t TestingT, actual, expected interface{}) {
+	if expected != actual {
+		t.Fatalf("Expected '%v' (%T) got '%v' (%T)", expected, expected, actual, actual)
+	}
+}
+
+// NilError asserts that the error is nil, otherwise it fails the test.
+func NilError(t TestingT, err error) {
+	if err != nil {
+		t.Fatalf("Expected no error, got: %s", err.Error())
+	}
+}
+
+// Error asserts that error is not nil, and contains the expected text,
+// otherwise it fails the test.
+func Error(t TestingT, err error, contains string) {
+	if err == nil {
+		t.Fatalf("Expected an error, but error was nil")
+	}
+
+	if !strings.Contains(err.Error(), contains) {
+		t.Fatalf("Expected error to contain '%s', got '%s'", contains, err.Error())
+	}
+}
+
+// Contains asserts that the string contains a substring, otherwise it fails the
+// test.
+func Contains(t TestingT, actual, contains string) {
+	if !strings.Contains(actual, contains) {
+		t.Fatalf("Expected '%s' to contain '%s'", actual, contains)
+	}
+}

testutil/pkg.go

@@ -0,0 +1 @@
+package testutil