add more rules to dangerfile (#1703)

* upgrade danger.js to latest version

* If PR contains tests using assert, suggest expect syntax

* if PR touches service, check service tester also touched

dangerfile.js

@@ -91,3 +91,29 @@ if (capitals.created || underscores.created) {
     '(dash-separated lowercase).',
   ].join(''));
 }
+
+const all_files = danger.git.created_files.concat(danger.git.modified_files);
+
+all_files.forEach(function(file) {
+  danger.git.diffForFile(file).then(function(diff) {
+    if (/\+.*assert[(.]/.test(diff.diff)) {
+      warn([
+        `Found 'assert' statement added in ${file}. `,
+        'Please ensure tests are written using Chai ',
+        '[expect syntax](http://chaijs.com/guide/styles/#expect)'
+      ].join(''));
+    }
+  });
+});
+
+all_files.forEach(function(file) {
+  if (/^services\/.+\/.+\.js$/.test(file) && file.endsWith('.js') && !file.endsWith('.tester.js')) {
+    const tester = file.replace('.js', '.tester.js');
+    if (all_files.indexOf(tester) == -1) {
+      warn([
+        `This PR modified ${file} but not ${tester}. `,
+        "That's okay so long as it's refactoring existing code.",
+      ].join(''));
+    }
+  }
+});