New srverrors package added. New error handling added to control package

internal/server/srverrors/error.go

@@ -0,0 +1,19 @@
+package srverrors
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+type ServerErrMessage struct {
+	Reason string
+}
+
+func WriteErrorResponse(statusCode int, reasonMsg string, res http.ResponseWriter) {
+	respBody := ServerErrMessage{}
+	respBody.Reason = reasonMsg
+	bb, _ := json.Marshal(respBody)
+	res.Header().Add("Content-Type", "application/json; charset=utf-8")
+	res.WriteHeader(statusCode)
+	_, _ = res.Write(bb)
+}

internal/server/srverrors/error_test.go

@@ -0,0 +1,47 @@
+package srverrors_test
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/BBVA/kapow/internal/server/srverrors"
+)
+
+func TestWriteErrorResponseSetsAppJsonContentType(t *testing.T) {
+	w := httptest.NewRecorder()
+
+	srverrors.WriteErrorResponse(0, "Not Important Here", w)
+
+	if v := w.Result().Header.Get("Content-Type"); v != "application/json; charset=utf-8" {
+		t.Errorf("Content-Type header mismatch. Expected: %q, got: %q", "application/json; charset=utf-8", v)
+	}
+}
+
+func TestWriteErrorResponseSetsRequestedStatusCode(t *testing.T) {
+	w := httptest.NewRecorder()
+
+	srverrors.WriteErrorResponse(http.StatusGone, "Not Important Here", w)
+
+	if v := w.Result().StatusCode; v != http.StatusGone {
+		t.Errorf("Status code mismatch. Expected: %d, got: %d", http.StatusGone, v)
+	}
+}
+
+func TestWriteErrorResponseSetsBodyCorrectly(t *testing.T) {
+	expectedReason := "Something Not Found"
+	w := httptest.NewRecorder()
+
+	srverrors.WriteErrorResponse(http.StatusNotFound, expectedReason, w)
+
+	errMsg := srverrors.ServerErrMessage{}
+	if bodyBytes, err := ioutil.ReadAll(w.Result().Body); err != nil {
+		t.Errorf("Unexpected error reading response body: %v", err)
+	} else if err := json.Unmarshal(bodyBytes, &errMsg); err != nil {
+		t.Errorf("Response body contains invalid JSON entity: %v", err)
+	} else if errMsg.Reason != expectedReason {
+		t.Errorf("Unexpected reason in response. Expected: %q, got: %q", expectedReason, errMsg.Reason)
+	}
+}