elastic: more tests (#68533)

* elastic: more tests

* fix lint error

pkg/tsdb/elasticsearch/client/client_test.go

@@ -111,6 +111,104 @@ func TestClient_ExecuteMultisearch(t *testing.T) {
 	})
 }
 
+func TestClient_Index(t *testing.T) {
+	tt := []struct {
+		name                string
+		indexInDatasource   string
+		patternInDatasource string
+		indexInRequest      []string
+	}{
+		{
+			name:                "single string",
+			indexInDatasource:   "logs-*",
+			patternInDatasource: "",
+			indexInRequest:      []string{"logs-*"},
+		},
+		{
+			name:                "daily pattern",
+			indexInDatasource:   "[logs-]YYYY.MM.DD",
+			patternInDatasource: "Daily",
+			indexInRequest:      []string{"logs-2018.05.10", "logs-2018.05.11", "logs-2018.05.12"},
+		},
+	}
+
+	for _, test := range tt {
+		t.Run(test.name, func(t *testing.T) {
+			var request *http.Request
+			var requestBody *bytes.Buffer
+
+			ts := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+				request = r
+				buf, err := io.ReadAll(r.Body)
+				require.NoError(t, err)
+
+				requestBody = bytes.NewBuffer(buf)
+
+				rw.Header().Set("Content-Type", "application/x-ndjson")
+				_, err = rw.Write([]byte(
+					`{
+				"responses": [
+					{
+						"hits": {	"hits": [], "max_score": 0,	"total": { "value": 4656, "relation": "eq"}	},
+						"status": 200
+					}
+				]
+			}`))
+				require.NoError(t, err)
+				rw.WriteHeader(200)
+			}))
+
+			configuredFields := ConfiguredFields{
+				TimeField:       "testtime",
+				LogMessageField: "line",
+				LogLevelField:   "lvl",
+			}
+
+			ds := DatasourceInfo{
+				URL:                        ts.URL,
+				HTTPClient:                 ts.Client(),
+				Database:                   test.indexInDatasource,
+				ConfiguredFields:           configuredFields,
+				Interval:                   test.patternInDatasource,
+				MaxConcurrentShardRequests: 6,
+				IncludeFrozen:              true,
+				XPack:                      true,
+			}
+
+			from := time.Date(2018, 5, 10, 17, 50, 0, 0, time.UTC)
+			to := time.Date(2018, 5, 12, 17, 55, 0, 0, time.UTC)
+			timeRange := backend.TimeRange{
+				From: from,
+				To:   to,
+			}
+
+			c, err := NewClient(context.Background(), &ds, timeRange)
+			require.NoError(t, err)
+			require.NotNil(t, c)
+
+			t.Cleanup(func() {
+				ts.Close()
+			})
+
+			ms, err := createMultisearchForTest(t, c)
+			require.NoError(t, err)
+			_, err = c.ExecuteMultisearch(ms)
+			require.NoError(t, err)
+
+			require.NotNil(t, request)
+			require.NotNil(t, requestBody)
+
+			headerBytes, err := requestBody.ReadBytes('\n')
+			require.NoError(t, err)
+
+			jHeader, err := simplejson.NewJson(headerBytes)
+			require.NoError(t, err)
+
+			assert.Equal(t, test.indexInRequest, jHeader.Get("index").MustStringArray())
+		})
+	}
+}
+
 func createMultisearchForTest(t *testing.T, c Client) (*MultiSearchRequest, error) {
 	t.Helper()