Extract api package

This is the first step towards genericizing the google_auth_proxy to support
OAuth2 providers other than Google as discussed in #65. The `api` package will
enable multiple providers to use the same `api.Request()` implementation.

api/api_test.go

@@ -0,0 +1,68 @@
+package api
+
+import (
+	"github.com/bitly/go-simplejson"
+	"github.com/bmizerany/assert"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func testBackend(response_code int, payload string) *httptest.Server {
+	return httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(response_code)
+			w.Write([]byte(payload))
+		}))
+}
+
+func TestRequest(t *testing.T) {
+	backend := testBackend(200, "{\"foo\": \"bar\"}")
+	defer backend.Close()
+
+	req, _ := http.NewRequest("GET", backend.URL, nil)
+	response, err := Request(req)
+	assert.Equal(t, nil, err)
+	result, err := response.Get("foo").String()
+	assert.Equal(t, nil, err)
+	assert.Equal(t, "bar", result)
+}
+
+func TestRequestFailure(t *testing.T) {
+	// Create a backend to generate a test URL, then close it to cause a
+	// connection error.
+	backend := testBackend(200, "{\"foo\": \"bar\"}")
+	backend.Close()
+
+	req, err := http.NewRequest("GET", backend.URL, nil)
+	assert.Equal(t, nil, err)
+	resp, err := Request(req)
+	assert.Equal(t, (*simplejson.Json)(nil), resp)
+	assert.NotEqual(t, nil, err)
+	if !strings.HasSuffix(err.Error(), "connection refused") {
+		t.Error("expected error when a connection fails")
+	}
+}
+
+func TestHttpErrorCode(t *testing.T) {
+	backend := testBackend(404, "{\"foo\": \"bar\"}")
+	defer backend.Close()
+
+	req, err := http.NewRequest("GET", backend.URL, nil)
+	assert.Equal(t, nil, err)
+	resp, err := Request(req)
+	assert.Equal(t, (*simplejson.Json)(nil), resp)
+	assert.NotEqual(t, nil, err)
+}
+
+func TestJsonParsingError(t *testing.T) {
+	backend := testBackend(200, "not well-formed JSON")
+	defer backend.Close()
+
+	req, err := http.NewRequest("GET", backend.URL, nil)
+	assert.Equal(t, nil, err)
+	resp, err := Request(req)
+	assert.Equal(t, (*simplejson.Json)(nil), resp)
+	assert.NotEqual(t, nil, err)
+}