Add sourcemap support for testing

Closes #196

PiperOrigin-RevId: 195188262
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 5c23f73..00ea325 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -14,3 +14,4 @@
 Bowen Ni <bowen1897@gmail.com>
 Daniel Muller <mrmeku@gmail.com>
 Martin Probst <martin@probst.io>
+Eric Stolten <stoltene2@gmail.com>
diff --git a/internal/karma/karma.conf.js b/internal/karma/karma.conf.js
index a134cc4..7dc841d 100644
--- a/internal/karma/karma.conf.js
+++ b/internal/karma/karma.conf.js
@@ -70,7 +70,10 @@
   }
 
   config.set({
-    plugins: ['karma-*', 'karma-concat-js'],
+    plugins: ['karma-*', 'karma-concat-js', 'karma-sourcemap-loader'],
+    preprocessors: {
+      '**/*.js': ['sourcemap']
+    },
     frameworks: ['jasmine', 'concat_js'],
 
     // test results reporter to use
diff --git a/internal/karma/package.json b/internal/karma/package.json
index 52d0091..c6f4d42 100644
--- a/internal/karma/package.json
+++ b/internal/karma/package.json
@@ -5,6 +5,7 @@
     "karma": "alexeagle/karma#fa1a84ac881485b5657cb669e9b4e5da77b79f0a",
     "karma-chrome-launcher": "2.2.0",
     "karma-jasmine": "1.1.1",
+    "karma-sourcemap-loader": "0.3.7",
     "karma-requirejs": "1.1.0",
     "puppeteer": "1.1.0",
     "requirejs": "2.3.5",
diff --git a/internal/karma/yarn.lock b/internal/karma/yarn.lock
index 7a576fe..16c8fe5 100644
--- a/internal/karma/yarn.lock
+++ b/internal/karma/yarn.lock
@@ -1242,6 +1242,12 @@
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/karma-requirejs/-/karma-requirejs-1.1.0.tgz#fddae2cb87d7ebc16fb0222893564d7fee578798"
 
+karma-sourcemap-loader@0.3.7:
+  version "0.3.7"
+  resolved "https://registry.yarnpkg.com/karma-requirejs/-/karma-sourcemap-loader-0.3.7.tgz#91322c77f8f13d46fed062b042e1009d4c4505d8"
+  dependencies:
+    graceful-fs "^4.1.2"
+
 karma@alexeagle/karma#fa1a84ac881485b5657cb669e9b4e5da77b79f0a:
   version "1.7.1"
   resolved "https://codeload.github.com/alexeagle/karma/tar.gz/fa1a84ac881485b5657cb669e9b4e5da77b79f0a"