Add package: jsonhelper

Author: hioki-daichi

kadai4/hioki-daichi/jsonhelper/jsonhelper.go

@@ -0,0 +1,30 @@
+/*
+Package jsonhelper is a collection of convenient functions for manipulating JSON.
+*/
+package jsonhelper
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+)
+
+// ToJSON converts v to JSON.
+func ToJSON(v interface{}) (string, error) {
+	var buf bytes.Buffer
+	encoder := newEncoderFunc(&buf)
+	if err := encoder.Encode(v); err != nil {
+		return "", err
+	}
+	return buf.String(), nil
+}
+
+// for testing
+type encoder interface {
+	Encode(v interface{}) error
+}
+
+// for testing
+var newEncoderFunc = func(w io.Writer) encoder {
+	return json.NewEncoder(w)
+}

kadai4/hioki-daichi/jsonhelper/jsonhelper_test.go

@@ -0,0 +1,43 @@
+package jsonhelper
+
+import (
+	"errors"
+	"io"
+	"testing"
+)
+
+func TestJsonhelper_ToJSON(t *testing.T) {
+	foo := struct {
+		Bar string `json:"bar"`
+		Baz int    `json:"baz"`
+	}{
+		Bar: "barbar",
+		Baz: 1,
+	}
+
+	actual, err := ToJSON(foo)
+	if err != nil {
+		t.Fatalf("err %s", err)
+	}
+	expected := "{\"bar\":\"barbar\",\"baz\":1}\n"
+	if actual != expected {
+		t.Errorf(`unexpected : expected: "%s" actual: "%s"`, expected, actual)
+	}
+}
+
+func TestJsonhelper_ToJSON_Error(t *testing.T) {
+	expected := errInMock
+
+	newEncoderFunc = func(w io.Writer) encoder { return &mockEncoder{} }
+
+	_, actual := ToJSON(struct{}{})
+	if actual != expected {
+		t.Errorf(`unexpected : expected: "%s" actual: "%s"`, expected, actual)
+	}
+}
+
+var errInMock = errors.New("error in mock")
+
+type mockEncoder struct{}
+
+func (m *mockEncoder) Encode(v interface{}) error { return errInMock }