Bug 1470151 - Add a PerTestCoverageUtils JavaScript module to manage resetting/dumping coverage counters for tests. r=jmaher

tools/code-coverage/PerTestCoverageUtils.jsm

@@ -0,0 +1,64 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* exported PerTestCoverageUtils */
+
+"use strict";
+
+var EXPORTED_SYMBOLS = ["PerTestCoverageUtils"];
+
+ChromeUtils.defineModuleGetter(this, "Services", "resource://gre/modules/Services.jsm");
+
+class PerTestCoverageUtilsClass {
+  constructor(tmp_gcov_dir, gcov_dir) {
+    this.tmp_gcov_dir = tmp_gcov_dir;
+    this.gcov_dir = gcov_dir;
+
+    this.codeCoverageService = Cc["@mozilla.org/tools/code-coverage;1"].getService(Ci.nsICodeCoverage);
+  }
+
+  _awaitPromise(promise) {
+    let ret;
+    let complete = false;
+    let error = null;
+    promise.catch(e => error = e).then(v => {
+      ret = v;
+      complete = true;
+    });
+    Services.tm.spinEventLoopUntil(() => complete);
+    if (error) {
+      throw new Error(error);
+    }
+    return ret;
+  }
+
+  // Resets the counters to 0.
+  beforeTest() {
+    this._awaitPromise(this.codeCoverageService.resetCounters());
+  }
+
+  // Dumps counters and moves the gcda files in the directory expected by codecoverage.py.
+  afterTest() {
+    this._awaitPromise(this.codeCoverageService.dumpCounters());
+
+    let srcDir = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+    srcDir.initWithPath(this.tmp_gcov_dir);
+
+    let destDir = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+    destDir.initWithPath(this.gcov_dir);
+
+    let srcDirEntries = srcDir.directoryEntries;
+    while (srcDirEntries.hasMoreElements()) {
+      srcDirEntries.nextFile.moveTo(destDir, null);
+    }
+  }
+}
+
+const env = Cc["@mozilla.org/process/environment;1"].getService(Ci.nsIEnvironment);
+// This is the directory where gcov is emitting the gcda files.
+const tmp_gcov_dir = env.get("GCOV_PREFIX");
+// This is the directory where codecoverage.py is expecting to see the gcda files.
+const gcov_dir = env.get("GCOV_RESULTS_DIR");
+
+const PerTestCoverageUtils = gcov_dir ? new PerTestCoverageUtilsClass(tmp_gcov_dir, gcov_dir) : null;

tools/code-coverage/moz.build

@@ -31,4 +31,6 @@ if CONFIG['MOZ_CODE_COVERAGE']:
     XPCSHELL_TESTS_MANIFESTS += ['tests/xpcshell/xpcshell.ini']
     MOCHITEST_MANIFESTS += ['tests/mochitest/mochitest.ini']
 
+    TESTING_JS_MODULES += ['PerTestCoverageUtils.jsm']
+
     FINAL_LIBRARY = 'xul'