diff --git a/public/app/plugins/datasource/prometheus/specs/datasource.jest.ts b/public/app/plugins/datasource/prometheus/specs/datasource.jest.ts
new file mode 100644
index 00000000000..cca74e023e7
--- /dev/null
+++ b/public/app/plugins/datasource/prometheus/specs/datasource.jest.ts
@@ -0,0 +1,104 @@
+import _ from 'lodash';
+import moment from 'moment';
+import q from 'q';
+import { PrometheusDatasource } from '../datasource';
+
+describe('PrometheusDatasource', () => {
+  let ctx: any = {};
+  let instanceSettings = {
+    url: 'proxied',
+    directUrl: 'direct',
+    user: 'test',
+    password: 'mupp',
+    jsonData: {},
+  };
+
+  ctx.backendSrvMock = {};
+  ctx.templateSrvMock = {
+    replace: a => a,
+  };
+  ctx.timeSrvMock = {};
+
+  beforeEach(() => {
+    ctx.ds = new PrometheusDatasource(instanceSettings, q, ctx.backendSrvMock, ctx.templateSrvMock, ctx.timeSrvMock);
+  });
+
+  describe('When converting prometheus histogram to heatmap format', () => {
+    beforeEach(() => {
+      ctx.query = {
+        range: { from: moment(1443454528000), to: moment(1443454528000) },
+        targets: [{ expr: 'test{job="testjob"}', format: 'heatmap', legendFormat: '{{le}}' }],
+        interval: '60s',
+      };
+    });
+
+    it('should convert cumullative histogram to ordinary', () => {
+      const resultMock = [
+        {
+          metric: { __name__: 'metric', job: 'testjob', le: '10' },
+          values: [[1443454528.0, '10'], [1443454528.0, '10']],
+        },
+        {
+          metric: { __name__: 'metric', job: 'testjob', le: '20' },
+          values: [[1443454528.0, '20'], [1443454528.0, '10']],
+        },
+        {
+          metric: { __name__: 'metric', job: 'testjob', le: '30' },
+          values: [[1443454528.0, '25'], [1443454528.0, '10']],
+        },
+      ];
+      const responseMock = { data: { data: { result: resultMock } } };
+
+      const expected = [
+        {
+          target: '10',
+          datapoints: [[10, 1443454528000], [10, 1443454528000]],
+        },
+        {
+          target: '20',
+          datapoints: [[10, 1443454528000], [0, 1443454528000]],
+        },
+        {
+          target: '30',
+          datapoints: [[5, 1443454528000], [0, 1443454528000]],
+        },
+      ];
+
+      ctx.ds.performTimeSeriesQuery = jest.fn().mockReturnValue(responseMock);
+      return ctx.ds.query(ctx.query).then(result => {
+        let results = result.data;
+        return expect(results).toEqual(expected);
+      });
+    });
+
+    it('should sort series by label value', () => {
+      const resultMock = [
+        {
+          metric: { __name__: 'metric', job: 'testjob', le: '2' },
+          values: [[1443454528.0, '10'], [1443454528.0, '10']],
+        },
+        {
+          metric: { __name__: 'metric', job: 'testjob', le: '4' },
+          values: [[1443454528.0, '20'], [1443454528.0, '10']],
+        },
+        {
+          metric: { __name__: 'metric', job: 'testjob', le: '+Inf' },
+          values: [[1443454528.0, '25'], [1443454528.0, '10']],
+        },
+        {
+          metric: { __name__: 'metric', job: 'testjob', le: '1' },
+          values: [[1443454528.0, '25'], [1443454528.0, '10']],
+        },
+      ];
+      const responseMock = { data: { data: { result: resultMock } } };
+
+      const expected = ['1', '2', '4', '+Inf'];
+
+      ctx.ds.performTimeSeriesQuery = jest.fn().mockReturnValue(responseMock);
+      return ctx.ds.query(ctx.query).then(result => {
+        let seriesLabels = _.map(result.data, 'target');
+        return expect(seriesLabels).toEqual(expected);
+      });
+    });
+  });
+});