fs_test: Add testing for WriteJSON

Signed-off-by: Simarpreet Singh <simar@linux.com>

utils/fs_test.go

@@ -0,0 +1,110 @@
+package utils
+
+import (
+	"errors"
+	"io/ioutil"
+	"math"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+)
+
+type fakeMemFS struct {
+	create func(string) (afero.File, error)
+}
+
+func (ffs fakeMemFS) Create(name string) (afero.File, error) {
+	if ffs.create != nil {
+		return ffs.create(name)
+	}
+
+	return ioutil.TempFile("", "fakeMemFS-*.file")
+}
+
+func (ffs fakeMemFS) Mkdir(name string, perm os.FileMode) error {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) MkdirAll(path string, perm os.FileMode) error {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) Open(name string) (afero.File, error) {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) OpenFile(name string, flag int, perm os.FileMode) (afero.File, error) {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) Remove(name string) error {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) RemoveAll(path string) error {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) Rename(oldname, newname string) error {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) Stat(name string) (os.FileInfo, error) {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) Name() string {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) Chmod(name string, mode os.FileMode) error {
+	panic("implement me")
+}
+
+func (ffs fakeMemFS) Chtimes(name string, atime time.Time, mtime time.Time) error {
+	panic("implement me")
+}
+
+func TestFs_WriteJSON(t *testing.T) {
+	testCases := []struct {
+		name          string
+		memfs         Fs
+		inputData     interface{}
+		expectedError error
+	}{
+		{
+			name:      "happy path",
+			memfs:     NewFs(fakeMemFS{}),
+			inputData: `{}`,
+		},
+		{
+			name: "sad path: fs.AppFs.Create returns an error",
+			memfs: NewFs(fakeMemFS{
+				create: func(s string) (file afero.File, e error) {
+					return nil, errors.New("cannot create file")
+				},
+			}),
+			expectedError: errors.New("unable to open a file: cannot create file"),
+		},
+		{
+			name:          "sad path: bad json input data",
+			memfs:         NewFs(fakeMemFS{}),
+			inputData:     math.NaN(),
+			expectedError: errors.New("failed to marshal JSON: json: unsupported value: NaN"),
+		},
+	}
+
+	for _, tc := range testCases {
+		err := tc.memfs.WriteJSON("foo", tc.inputData)
+		switch {
+		case tc.expectedError != nil:
+			assert.Equal(t, tc.expectedError.Error(), err.Error(), tc.name)
+		default:
+			assert.NoError(t, err, tc.name)
+		}
+	}
+
+}