diff --git a/devtools/client/inspector/markup/test/browser_markup_events_03.js b/devtools/client/inspector/markup/test/browser_markup_events_03.js
index 85efc7e54a4d..be49c2849648 100644
--- a/devtools/client/inspector/markup/test/browser_markup_events_03.js
+++ b/devtools/client/inspector/markup/test/browser_markup_events_03.js
@@ -23,7 +23,7 @@ const TEST_DATA = [ // eslint-disable-line
           "Bubbling",
           "DOM2"
         ],
-        handler: "function es6Method(foo, bar) {\n" +
+        handler: "es6Method(foo, bar) {\n" +
                  "  alert(\"obj.es6Method\");\n" +
                  "}"
       }
diff --git a/devtools/client/webconsole/test/browser_webconsole_output_02.js b/devtools/client/webconsole/test/browser_webconsole_output_02.js
index 4c61cf041635..837ec673c411 100644
--- a/devtools/client/webconsole/test/browser_webconsole_output_02.js
+++ b/devtools/client/webconsole/test/browser_webconsole_output_02.js
@@ -24,7 +24,7 @@ var inputTests = [
   {
     input: "(function() { return 42; })",
     output: "function ()",
-    printOutput: "function () { return 42; }",
+    printOutput: "function() { return 42; }",
     suppressClick: true
   },
 
@@ -40,7 +40,7 @@ var inputTests = [
   {
     input: "testobj1.testfn2",
     output: "function testfn2()",
-    printOutput: "function () { return 42; }",
+    printOutput: "function() { return 42; }",
     suppressClick: true
   },
 
diff --git a/devtools/server/tests/unit/test_listsources-04.js b/devtools/server/tests/unit/test_listsources-04.js
index 6da99a6cec1c..8e1a57bf027f 100644
--- a/devtools/server/tests/unit/test_listsources-04.js
+++ b/devtools/server/tests/unit/test_listsources-04.js
@@ -29,12 +29,12 @@ function run_test_with_server(server, cb) {
     addSources(debuggee);
 
     threadClient.getSources(Task.async(function* (res) {
-      do_check_true(res.sources.length === 3, "3 sources exist");
+      do_check_eq(res.sources.length, 3, "3 sources exist");
 
       yield threadClient.reconfigure({ useSourceMaps: false });
 
       threadClient.getSources(function(res) {
-        do_check_true(res.sources.length === 1, "1 source exist");
+        do_check_eq(res.sources.length, 1, "1 source exist");
         client.close().then(cb);
       });
     }));