Enforce presence of "x", "y", and "y2" axes

Certain aspects of the frontend requires the presence of these three
axes, so part of the contract established is that the backend will
always provide them. Since we centralize creation of
dashboardCellResponses, this is where these axes are added to all cell
responses.

Additionally, because there was previously no coverage over the
dashboard cells endpoints, a test has been added to cover the
DashboardCells method of Service.

mocks/dashboards.go

@@ -0,0 +1,37 @@
+package mocks
+
+import (
+	"context"
+
+	"github.com/influxdata/chronograf"
+)
+
+var _ chronograf.DashboardsStore = &DashboardsStore{}
+
+type DashboardsStore struct {
+	AddF    func(ctx context.Context, newDashboard chronograf.Dashboard) (chronograf.Dashboard, error)
+	AllF    func(ctx context.Context) ([]chronograf.Dashboard, error)
+	DeleteF func(ctx context.Context, target chronograf.Dashboard) error
+	GetF    func(ctx context.Context, id chronograf.DashboardID) (chronograf.Dashboard, error)
+	UpdateF func(ctx context.Context, target chronograf.Dashboard) error
+}
+
+func (d *DashboardsStore) Add(ctx context.Context, newDashboard chronograf.Dashboard) (chronograf.Dashboard, error) {
+	return d.AddF(ctx, newDashboard)
+}
+
+func (d *DashboardsStore) All(ctx context.Context) ([]chronograf.Dashboard, error) {
+	return d.AllF(ctx)
+}
+
+func (d *DashboardsStore) Delete(ctx context.Context, target chronograf.Dashboard) error {
+	return d.DeleteF(ctx, target)
+}
+
+func (d *DashboardsStore) Get(ctx context.Context, id chronograf.DashboardID) (chronograf.Dashboard, error) {
+	return d.GetF(ctx, id)
+}
+
+func (d *DashboardsStore) Update(ctx context.Context, target chronograf.Dashboard) error {
+	return d.UpdateF(ctx, target)
+}

mocks/logger.go

@@ -3,6 +3,7 @@ package mocks
 import (
 	"fmt"
 	"io"
+	"testing"
 
 	"github.com/influxdata/chronograf"
 )
@@ -72,3 +73,11 @@ func (tl *TestLogger) stringifyArg(arg interface{}) []byte {
 		return []byte("UNKNOWN")
 	}
 }
+
+// Dump dumps out logs into a given testing.T's logs
+func (tl *TestLogger) Dump(t *testing.T) {
+	t.Log("== Dumping Test Logs ==")
+	for _, msg := range tl.Messages {
+		t.Logf("lvl: %s, msg: %s", msg.Level, msg.Body)
+	}
+}

server/cells.go

@@ -33,6 +33,20 @@ func newCellResponses(dID chronograf.DashboardID, dcells []chronograf.DashboardC
 		if len(cell.Queries) == 0 {
 			cell.Queries = make([]chronograf.DashboardQuery, 0)
 		}
+
+		// ensure x, y, and y2 axes always returned
+		labels := []string{"x", "y", "y2"}
+		if cell.Axes == nil {
+			cell.Axes = make(map[string]chronograf.Axis, len(labels))
+		}
+
+		for _, lbl := range labels {
+			_, found := cell.Axes[lbl]
+			if !found {
+				cell.Axes[lbl] = chronograf.Axis{}
+			}
+		}
+
 		cells[i] = dashboardCellResponse{
 			DashboardCell: cell,
 			Links: dashboardCellLinks{

server/cells_test.go

@@ -1,9 +1,18 @@
 package server_test
 
 import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
 	"testing"
 
+	"github.com/bouk/httprouter"
+	"github.com/google/go-cmp/cmp"
 	"github.com/influxdata/chronograf"
+	"github.com/influxdata/chronograf/mocks"
 	"github.com/influxdata/chronograf/server"
 )
 
@@ -58,3 +67,131 @@ func Test_Cells_CorrectAxis(t *testing.T) {
 		})
 	}
 }
+
+func Test_Service_DashboardCells(t *testing.T) {
+	cellsTests := []struct {
+		name         string
+		reqURL       *url.URL
+		ctxParams    map[string]string
+		mockResponse []chronograf.DashboardCell
+		expected     []chronograf.DashboardCell
+		expectedCode int
+	}{
+		{
+			"happy path",
+			&url.URL{
+				Path: "/chronograf/v1/dashboards/1/cells",
+			},
+			map[string]string{
+				"id": "1",
+			},
+			[]chronograf.DashboardCell{},
+			[]chronograf.DashboardCell{},
+			http.StatusOK,
+		},
+		{
+			"cell axes should always be \"x\", \"y\", and \"y2\"",
+			&url.URL{
+				Path: "/chronograf/v1/dashboards/1/cells",
+			},
+			map[string]string{
+				"id": "1",
+			},
+			[]chronograf.DashboardCell{
+				{
+					ID:      "3899be5a-f6eb-4347-b949-de2f4fbea859",
+					X:       0,
+					Y:       0,
+					W:       4,
+					H:       4,
+					Name:    "CPU",
+					Queries: []chronograf.DashboardQuery{},
+					Axes:    map[string]chronograf.Axis{},
+				},
+			},
+			[]chronograf.DashboardCell{
+				{
+					ID:      "3899be5a-f6eb-4347-b949-de2f4fbea859",
+					X:       0,
+					Y:       0,
+					W:       4,
+					H:       4,
+					Name:    "CPU",
+					Queries: []chronograf.DashboardQuery{},
+					Axes: map[string]chronograf.Axis{
+						"x":  chronograf.Axis{},
+						"y":  chronograf.Axis{},
+						"y2": chronograf.Axis{},
+					},
+				},
+			},
+			http.StatusOK,
+		},
+	}
+
+	for _, test := range cellsTests {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			// setup context with params
+			ctx := context.Background()
+			params := httprouter.Params{}
+			for k, v := range test.ctxParams {
+				params = append(params, httprouter.Param{k, v})
+			}
+			ctx = httprouter.WithParams(ctx, params)
+
+			// setup response recorder and request
+			rr := httptest.NewRecorder()
+			req := httptest.NewRequest("GET", test.reqURL.RequestURI(), strings.NewReader("")).WithContext(ctx)
+
+			// setup mock DashboardCells store and logger
+			tlog := &mocks.TestLogger{}
+			svc := &server.Service{
+				DashboardsStore: &mocks.DashboardsStore{
+					GetF: func(ctx context.Context, id chronograf.DashboardID) (chronograf.Dashboard, error) {
+						return chronograf.Dashboard{
+							ID:        chronograf.DashboardID(1),
+							Cells:     test.mockResponse,
+							Templates: []chronograf.Template{},
+							Name:      "empty dashboard",
+						}, nil
+					},
+				},
+				Logger: tlog,
+			}
+
+			// invoke DashboardCell handler
+			svc.DashboardCells(rr, req)
+
+			// setup frame to decode response into
+			respFrame := []struct {
+				chronograf.DashboardCell
+				Links json.RawMessage `json:"links"` // ignore links
+			}{}
+
+			// decode response
+			resp := rr.Result()
+
+			if resp.StatusCode != test.expectedCode {
+				tlog.Dump(t)
+				t.Fatalf("%q - Status codes do not match. Want %d (%s), Got %d (%s)", test.name, test.expectedCode, http.StatusText(test.expectedCode), resp.StatusCode, http.StatusText(resp.StatusCode))
+			}
+
+			if err := json.NewDecoder(resp.Body).Decode(&respFrame); err != nil {
+				t.Fatalf("%q - Error unmarshaling response body: err: %s", test.name, err)
+			}
+
+			// extract actual
+			actual := []chronograf.DashboardCell{}
+			for _, rsp := range respFrame {
+				actual = append(actual, rsp.DashboardCell)
+			}
+
+			// compare actual and expected
+			if !cmp.Equal(actual, test.expected) {
+				t.Fatalf("%q - Dashboard Cells do not match: diff: %s", test.name, cmp.Diff(actual, test.expected))
+			}
+		})
+	}
+}

server/dashboards_test.go

@@ -273,6 +273,7 @@ func Test_newDashboardResponse(t *testing.T) {
 								"y": chronograf.Axis{
 									Bounds: []string{"2", "95"},
 								},
+								"y2": chronograf.Axis{},
 							},
 						},
 					},
@@ -284,6 +285,11 @@ func Test_newDashboardResponse(t *testing.T) {
 							ID: "b",
 							W:  4,
 							H:  4,
+							Axes: map[string]chronograf.Axis{
+								"x":  chronograf.Axis{},
+								"y":  chronograf.Axis{},
+								"y2": chronograf.Axis{},
+							},
 							Queries: []chronograf.DashboardQuery{
 								{
 									Command: "SELECT winning_horses from grays_sports_alamanc where time > now() - 15m",