add test for prometheus fill null

public/app/plugins/datasource/prometheus/specs/datasource_specs.ts

@@ -49,6 +49,73 @@ describe('PrometheusDatasource', function() {
       expect(results.data[0].target).to.be('test{job="testjob"}');
     });
   });
+  describe('When querying prometheus with one target which return multiple series', function() {
+    var results;
+    var start = 1443438675;
+    var end = 1443460275;
+    var step = 60;
+    var urlExpected = 'proxied/api/v1/query_range?query=' +
+                      encodeURIComponent('test{job="testjob"}') +
+                      '&start=' + start + '&end=' + end + '&step=' + step;
+    var query = {
+      range: { from: moment(1443438674760), to: moment(1443460274760) },
+      targets: [{ expr: 'test{job="testjob"}' }],
+      interval: '60s'
+    };
+    var response = {
+      status: "success",
+      data: {
+        resultType: "matrix",
+        result: [
+          {
+            metric: {"__name__": "test", job: "testjob", series: 'series 1'},
+            values: [
+              [start + step * 1, "3846"],
+              [start + step * 3, "3847"],
+              [end - step * 1, "3848"],
+            ]
+          },
+          {
+            metric: {"__name__": "test", job: "testjob", series: 'series 2'},
+            values: [
+              [start + step * 2, "4846"]
+            ]
+          },
+        ]
+      }
+    };
+    beforeEach(function() {
+      ctx.$httpBackend.expect('GET', urlExpected).respond(response);
+      ctx.ds.query(query).then(function(data) { results = data; });
+      ctx.$httpBackend.flush();
+    });
+    it('should be same length', function() {
+      expect(results.data.length).to.be(2);
+      expect(results.data[0].datapoints.length).to.be((end - start) / step + 1);
+      expect(results.data[1].datapoints.length).to.be((end - start) / step + 1);
+    });
+    it('should fill null until first datapoint in response', function() {
+      expect(results.data[0].datapoints[0][1]).to.be(start * 1000);
+      expect(results.data[0].datapoints[0][0]).to.be(null);
+      expect(results.data[0].datapoints[1][1]).to.be((start + step * 1) * 1000);
+      expect(results.data[0].datapoints[1][0]).to.be(3846);
+    });
+    it('should fill null after last datapoint in response', function() {
+      var length = (end - start) / step + 1;
+      expect(results.data[0].datapoints[length-2][1]).to.be((end - step * 1) * 1000);
+      expect(results.data[0].datapoints[length-2][0]).to.be(3848);
+      expect(results.data[0].datapoints[length-1][1]).to.be(end * 1000);
+      expect(results.data[0].datapoints[length-1][0]).to.be(null);
+    });
+    it('should fill null at gap between series', function() {
+      expect(results.data[0].datapoints[2][1]).to.be((start + step * 2) * 1000);
+      expect(results.data[0].datapoints[2][0]).to.be(null);
+      expect(results.data[1].datapoints[1][1]).to.be((start + step * 1) * 1000);
+      expect(results.data[1].datapoints[1][0]).to.be(null);
+      expect(results.data[1].datapoints[3][1]).to.be((start + step * 3) * 1000);
+      expect(results.data[1].datapoints[3][0]).to.be(null);
+    });
+  });
   describe('When performing metricFindQuery', function() {
     var results;
     var response;