Simplify Go Endpoints + Add Tests (#120)

This MR represents a major refactor of the Go codebase, as well as introducing tests for the handlers. The MR also introduces an endpoint to shutdown or restart the Go server, which may be useful for clients who want to refresh the state of the plugin after checking out branches. Finally, this MR adds a contributing document for users who want to make feature changes.

cmd/job_test.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"net/http"
+	"testing"
+
+	"github.com/xanzy/go-gitlab"
+)
+
+func getTraceFile(pid interface{}, jobID int, options ...gitlab.RequestOptionFunc) (*bytes.Reader, *gitlab.Response, error) {
+	return bytes.NewReader([]byte("Some data")), makeResponse(http.StatusOK), nil
+}
+
+func getTraceFileErr(pid interface{}, jobID int, options ...gitlab.RequestOptionFunc) (*bytes.Reader, *gitlab.Response, error) {
+	return nil, nil, errors.New("Some error from Gitlab")
+}
+
+func getTraceFileNon200(pid interface{}, jobID int, options ...gitlab.RequestOptionFunc) (*bytes.Reader, *gitlab.Response, error) {
+	return nil, makeResponse(http.StatusSeeOther), nil
+}
+
+func TestJobHandler(t *testing.T) {
+	t.Run("Should read a job trace file", func(t *testing.T) {
+		request := makeRequest(t, http.MethodGet, "/job", JobTraceRequest{})
+		server, _ := createRouterAndApi(fakeClient{getTraceFile: getTraceFile})
+		data := serveRequest(t, server, request, JobTraceResponse{})
+		assert(t, data.SuccessResponse.Message, "Log file read")
+		assert(t, data.SuccessResponse.Status, http.StatusOK)
+		assert(t, data.File, "Some data")
+	})
+
+	t.Run("Disallows non-GET methods", func(t *testing.T) {
+		request := makeRequest(t, http.MethodPost, "/job", JobTraceRequest{})
+		server, _ := createRouterAndApi(fakeClient{getTraceFile: getTraceFile})
+		data := serveRequest(t, server, request, ErrorResponse{})
+		checkBadMethod(t, *data, http.MethodGet)
+	})
+
+	t.Run("Should handle errors from Gitlab", func(t *testing.T) {
+		request := makeRequest(t, http.MethodGet, "/job", JobTraceRequest{})
+		server, _ := createRouterAndApi(fakeClient{getTraceFile: getTraceFileErr})
+		data := serveRequest(t, server, request, ErrorResponse{})
+		checkErrorFromGitlab(t, *data, "Could not get trace file for job")
+	})
+
+	t.Run("Should handle non-200s", func(t *testing.T) {
+		request := makeRequest(t, http.MethodGet, "/job", JobTraceRequest{})
+		server, _ := createRouterAndApi(fakeClient{getTraceFile: getTraceFileNon200})
+		data := serveRequest(t, server, request, ErrorResponse{})
+		checkNon200(t, *data, "Could not get trace file for job", "/job")
+	})
+}