1 files changed, 72 insertions, 0 deletions
diff --git a/devtools/shared/loader/browser-loader-mocks.js b/devtools/shared/loader/browser-loader-mocks.js
new file mode 100644
index 0000000000..d7d6ebed3f
--- /dev/null
+++ b/devtools/shared/loader/browser-loader-mocks.js
@@ -0,0 +1,72 @@
+/* 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/. */
+
+"use strict";
+
+// Map of mocked modules, keys are absolute URIs for devtools modules such as
+// "resource://devtools/path/to/mod.js, values are objects (anything passed to
+// setMockedModule technically).
+const _mocks = {};
+
+/**
+ * Retrieve a mocked module matching the provided uri, eg "resource://path/to/file.js".
+ */
+function getMockedModule(uri) {
+  return _mocks[uri];
+}
+exports.getMockedModule = getMockedModule;
+
+/**
+ * Module paths are transparently provided with or without ".js" when using the loader,
+ * normalize the user-provided module paths to always have modules ending with ".js".
+ */
+function _getUriForModulePath(modulePath) {
+  // Assume js modules and add the .js extension if missing.
+  if (!modulePath.endsWith(".js")) {
+    modulePath = modulePath + ".js";
+  }
+
+  // Add resource:// scheme if no scheme is specified.
+  if (!modulePath.includes("://")) {
+    modulePath = "resource://" + modulePath;
+  }
+
+  return modulePath;
+}
+
+/**
+ * Assign a mock object to the provided module path.
+ * @param mock
+ *        Plain JavaScript object that will implement the expected API for the mocked
+ *        module.
+ * @param modulePath
+ *        The module path should be the absolute module path, starting with `devtools`:
+ *        "devtools/client/some-panel/some-module"
+ */
+function setMockedModule(mock, modulePath) {
+  const uri = _getUriForModulePath(modulePath);
+  _mocks[uri] = new Proxy(mock, {
+    get(target, key) {
+      if (typeof target[key] === "function") {
+        // Functions are wrapped to be able to update the methods during the test, even if
+        // the methods were imported with destructuring. For instance:
+        //   `const { someMethod } = require("devtools/client/shared/my-module");`
+        return function() {
+          return target[key].apply(target, arguments);
+        };
+      }
+      return target[key];
+    },
+  });
+}
+exports.setMockedModule = setMockedModule;
+
+/**
+ * Remove any mock object defined for the provided absolute module path.
+ */
+function removeMockedModule(modulePath) {
+  const uri = _getUriForModulePath(modulePath);
+  delete _mocks[uri];
+}
+exports.removeMockedModule = removeMockedModule;