diff --git a/packages/jest-cli/src/generateEmptyCoverage.js b/packages/jest-cli/src/generateEmptyCoverage.js
index 55fab2c4105f..44a765c5b307 100644
--- a/packages/jest-cli/src/generateEmptyCoverage.js
+++ b/packages/jest-cli/src/generateEmptyCoverage.js
@@ -1,30 +1,29 @@
-/** 
- * Copyright (c) 2014-present, Facebook, Inc. All rights reserved. 
- * 
- * This source code is licensed under the BSD-style license found in the 
- * LICENSE file in the root directory of this source tree. An additional grant 
- * of patent rights can be found in the PATENTS file in the same directory. 
- * 
- * @flow 
- */ 
- 
-'use strict'; 
- 
-import type {Config, Path} from 'types/Config'; 
- 
-const IstanbulInstrument = require('istanbul-lib-instrument'); 
- 
-const {transformSource, shouldInstrument} = require('jest-runtime'); 
- 
-module.exports = function(source: string, filename: Path, config: Config) { 
-  if (shouldInstrument(filename, config)) { 
-    // Transform file without instrumentation first, to make sure produced 
-    // source code is ES6 (no flowtypes etc.) and can be instrumented 
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @flow
+ */
+'use strict';
+
+import type {Config, Path} from 'types/Config';
+
+const IstanbulInstrument = require('istanbul-lib-instrument');
+
+const {transformSource, shouldInstrument} = require('jest-runtime');
+
+module.exports = function(source: string, filename: Path, config: Config) {
+  if (shouldInstrument(filename, config)) {
+    // Transform file without instrumentation first, to make sure produced
+    // source code is ES6 (no flowtypes etc.) and can be instrumented
     source = transformSource(filename, config, source, false);
     const instrumenter = IstanbulInstrument.createInstrumenter();
-    instrumenter.instrumentSync(source, filename); 
+    instrumenter.instrumentSync(source, filename);
     return instrumenter.fileCoverage;
-  } else { 
+  } else {
     return null;
-  } 
-}; 
+  }
+};
diff --git a/packages/jest-cli/src/reporters/CoverageReporter.js b/packages/jest-cli/src/reporters/CoverageReporter.js
index a82b7b854b34..0f7326f4d597 100644
--- a/packages/jest-cli/src/reporters/CoverageReporter.js
+++ b/packages/jest-cli/src/reporters/CoverageReporter.js
@@ -9,7 +9,7 @@
 */
 'use strict';
 
-import type {AggregatedResult, CoverageMap, TestResult} from 'types/TestResult';
+import type {AggregatedResult, CoverageMap, SourceMapStore, TestResult} from 'types/TestResult';
 import type {Config} from 'types/Config';
 import type {RunnerContext} from 'types/Reporters';
 
@@ -19,7 +19,7 @@ const {clearLine} = require('jest-util');
 const {createReporter} = require('istanbul-api');
 const chalk = require('chalk');
 const fs = require('fs');
-const generateEmptyCoverage = require('../generateEmptyCoverage'); 
+const generateEmptyCoverage = require('../generateEmptyCoverage');
 const isCI = require('is-ci');
 const istanbulCoverage = require('istanbul-lib-coverage');
 const libSourceMaps = require('istanbul-lib-source-maps');
@@ -31,7 +31,7 @@ const isInteractive = process.stdout.isTTY && !isCI;
 
 class CoverageReporter extends BaseReporter {
   _coverageMap: CoverageMap;
-  _sourceMapStore: any;
+  _sourceMapStore: SourceMapStore;
 
   constructor() {
     super();
diff --git a/types/TestResult.js b/types/TestResult.js
index 9cb6b4b5019a..a74ada6ea851 100644
--- a/types/TestResult.js
+++ b/types/TestResult.js
@@ -10,20 +10,38 @@
 'use strict';
 
 import type {ConsoleBuffer} from './Console';
+import type {SourceMap} from './Transform';
 
-export type Coverage = {|
-  coveredSpans: Array<Object>,
-  uncoveredSpans: Array<Object>,
-  sourceText: string,
+export type FileCoverage = {|
+  path: string,
+  s: { [statementId: number]: number },
+  b: { [branchId: number]: number },
+  f: { [functionId: number]: number },
+  l: { [lineId: number]: number },
+  fnMap: { [functionId: number]: any },
+  statementMap: { [statementId: number]: any },
+  branchMap: { [branchId: number]: any },
+  inputSourceMap?: SourceMap,
 |};
 
+export type Coverage = {
+  [filePath: string]: FileCoverage,
+};
+
 export type CoverageMap = {|
   merge: (data: Object) => void,
   getCoverageSummary: () => Object,
-  data: Object,
-  addFileCoverage: (fileCoverage: Object) => void,
+  data: Coverage,
+  addFileCoverage: (fileCoverage: FileCoverage) => void,
 |};
 
+export class SourceMapStore {
+  transformCoverage: (coverageMap: CoverageMap) => {
+    map: CoverageMap,
+    sourceFinder: any
+  }
+}
+
 export type Error = {|
   message: string,
   stack: ?string,
diff --git a/types/Transform.js b/types/Transform.js
index da061bad0ad8..caf6f2336fd6 100644
--- a/types/Transform.js
+++ b/types/Transform.js
@@ -21,18 +21,6 @@ export type SourceMap = {|
   version: number,
 |};
 
-export type Coverage = {|
-  path: string,
-  s: { [statementId: number]: number },
-  b: { [branchId: number]: number },
-  f: { [functionId: number]: number },
-  l: { [lineId: number]: number },
-  fnMap: { [functionId: number]: any },
-  statementMap: { [statementId: number]: any },
-  branchMap: { [branchId: number]: any },
-  inputSourceMap: ?SourceMap,
-|}
-
 export type TransformOptions = {|
   instrument: boolean,
   watch: boolean,
@@ -54,11 +42,4 @@ export type Transformer = {|
     config: Config,
     options?: TransformOptions,
   ) => string,
-
-  getEmptyCoverage: (
-    sourceText: string,
-    sourcePath: Path,
-    config: Config,
-    options?: TransformOptions,
-  ) => Coverage
 |};