diff --git a/DEVELOPER.md b/DEVELOPER.md
index 7e148b0ffe..08f971fdcf 100644
--- a/DEVELOPER.md
+++ b/DEVELOPER.md
@@ -155,7 +155,7 @@ You can selectively run either the JS or Dart versions as follows:
 
 You can run just the unit tests as follows:
 
-* `$(npm bin)/gulp test.unit.js`: JS tests in a browser; runs in **watch mode** (i.e. karma
+* `$(npm bin)/gulp test.unit.js`: JS tests in a browser; runs in **watch mode** (i.e.
    watches the test files for changes and re-runs tests when files are updated).
 * `$(npm bin)/gulp test.unit.cjs`: JS tests in NodeJS; runs in **watch mode**.
 * `$(npm bin)/gulp test.unit.dart`: Dart tests in Dartium; runs in **watch mode**.
@@ -166,15 +166,14 @@ If you prefer running tests in "single-run" mode rather than watch mode use:
 * `$(npm bin)/gulp test.unit.cjs/ci`
 * `$(npm bin)/gulp test.unit.dart/ci`
 
+The task updates the dist folder with transpiled code whenever a source or test file changes, and
+Karma is run against the new output.
+
 **Note**: If you want to only run a single test you can alter the test you wish to run by changing
 `it` to `iit` or `describe` to `ddescribe`. This will only run that individual test and make it
 much easier to debug. `xit` and `xdescribe` can also be useful to exclude a test and a group of
 tests respectively.
 
-**Note for transpiler tests**: The karma preprocessor is setup in a way so that after every test
-run the transpiler is reloaded. With that it is possible to make changes to the preprocessor and
-run the tests without exiting karma (just touch a test file that you would like to run).
-
 ### E2e tests
 
 1. `$(npm bin)/gulp build.js.cjs` (builds benchpress and tests into `dist/js/cjs` folder).
diff --git a/karma.conf.js b/karma.conf.js
deleted file mode 120000
index a08489ffd8..0000000000
--- a/karma.conf.js
+++ /dev/null
@@ -1 +0,0 @@
-karma-js.conf.js
\ No newline at end of file
diff --git a/tools/transpiler/karma-traceur-preprocessor.js b/tools/transpiler/karma-traceur-preprocessor.js
deleted file mode 100644
index 49d8faa334..0000000000
--- a/tools/transpiler/karma-traceur-preprocessor.js
+++ /dev/null
@@ -1,56 +0,0 @@
-var transpiler = require('./index.js');
-
-module.exports = {
-  'preprocessor:traceur': ['factory', createJs2DartPreprocessor]
-};
-
-function createJs2DartPreprocessor(logger, basePath, config, emitter) {
-  var log = logger.create('traceur');
-  // Reload the transpiler sources so we don't need to
-  // restart karma when we made changes to traceur.
-  // As there is no event that is called before any preprocessor runs,
-  // we listen for the end event in karma to reload the
-  // transpiler sources.
-  emitter.on('run_complete', function(filesPromise) {
-    transpiler.reloadSources();
-  });
-  return function(content, file, done) {
-    try {
-      var moduleName = config.resolveModuleName(file.originalPath);
-      if (config.transformPath) {
-        file.path = config.transformPath(file.originalPath);
-      }
-
-      var result = transpiler.compile(config.options, {
-        inputPath: file.originalPath,
-        outputPath: file.path,
-        moduleName: moduleName
-      }, content, true);
-
-      var transpiledContent = result.js;
-      var sourceMap = result.sourceMap;
-
-      if (sourceMap) {
-        transpiledContent += '\n//# sourceMappingURL=data:application/json;charset=utf-8;base64,';
-        transpiledContent += new Buffer(JSON.stringify(sourceMap)).toString('base64') + '\n';
-        file.sourceMap = sourceMap;
-      }
-
-      done(null, transpiledContent);
-    } catch (errors) {
-      var errorString;
-      if (errors.forEach) {
-        errors.forEach(function(error) {
-          log.error(error);
-        });
-        errorString = errors.join('\n');
-      } else {
-        log.error(errors);
-        errorString = errors;
-      }
-      done(new Error('TRACEUR COMPILE ERRORS\n' + errorString));
-    }
-  };
-}
-
-createJs2DartPreprocessor.$inject = ['logger', 'config.basePath', 'config.traceurPreprocessor', 'emitter'];
diff --git a/tools/transpiler/karma-ts2dart-preprocessor.js b/tools/transpiler/karma-ts2dart-preprocessor.js
deleted file mode 100644
index d15fe09a24..0000000000
--- a/tools/transpiler/karma-ts2dart-preprocessor.js
+++ /dev/null
@@ -1,36 +0,0 @@
-// Transpiles JavaScript and TypeScript code to Dart using ts2dart.
-
-var ts2dart = require('ts2dart');
-var rundartpackage = require('../build/rundartpackage.js');
-
-module.exports = {
-  'preprocessor:ts2dart': ['factory', createTs2DartPreprocessor]
-};
-
-function createTs2DartPreprocessor(logger, basePath, config, emitter) {
-  var log = logger.create('ts2dart');
-  return function(content, file, done) {
-    try {
-      var moduleName = config.resolveModuleName(file.originalPath);
-      file.path = config.transformPath(file.originalPath);
-      var transpiler = new ts2dart.Transpiler(
-          {failFast: false, generateLibraryName: true, generateSourceMap: true});
-      var transpiledContent = transpiler.translateFile(file.originalPath, moduleName);
-      // TODO(martinprobst): Source maps.
-      done(null, transpiledContent);
-    } catch (errors) {
-      var errorString;
-      if (errors.forEach) {
-        errors.forEach(function(error) { log.error(error); });
-        errorString = errors.join('\n');
-      } else {
-        log.error(errors);
-        errorString = errors;
-      }
-      done(new Error('ts2dart compile errors:\n' + errorString));
-    }
-  };
-}
-
-createTs2DartPreprocessor
-    .$inject = ['logger', 'config.basePath', 'config.ts2dartPreprocessor', 'emitter'];