new file mode 100644
--- /dev/null
+++ b/editor/composer/test/.eslintrc.js
@@ -0,0 +1,8 @@
+"use strict";
+
+module.exports = {
+  "extends": [
+    "plugin:mozilla/chrome-test",
+    "plugin:mozilla/mochitest-test",
+  ]
+};

new file mode 100644
--- /dev/null
+++ b/editor/libeditor/tests/.eslintrc.js
@@ -0,0 +1,8 @@
+"use strict";
+
+module.exports = {
+  "extends": [
+    "plugin:mozilla/browser-test",
+    "plugin:mozilla/mochitest-test",
+  ]
+};

--- a/editor/libeditor/tests/test_resizers_resizing_elements.html
+++ b/editor/libeditor/tests/test_resizers_resizing_elements.html
@@ -113,16 +113,18 @@ SimpleTest.waitForFocus(async function()
     // needlessGrowth means that we change the size of a dimension perpendecular to
     // the mouse movement axis in order to preserve the aspect ratio.
     // reversedGrowth means that we change the size of a dimension in the opposite
     // direction to the mouse movement in order to maintain the aspect ratio.
     const ignoredGrowth = aPreserveRatio ? 0 : 1;
     const needlessGrowth = aPreserveRatio ? 1 : 0;
     const reversedGrowth = aPreserveRatio ? -1 : 1;
 
+    /* eslint-disable no-multi-spaces */
+
     // top resizer
     await testResizer(W/2,   0, -10, -10,   0,  10);
     await testResizer(W/2,   0, -10,   0,   0,   0);
     await testResizer(W/2,   0, -10,  10,   0, -10);
     await testResizer(W/2,   0,   0, -10,   0,  10);
     await testResizer(W/2,   0,   0,   0,   0,   0);
     await testResizer(W/2,   0,   0,  10,   0, -10);
     await testResizer(W/2,   0,  10, -10,   0,  10);
@@ -200,16 +202,18 @@ SimpleTest.waitForFocus(async function()
     await testResizer(  0,   0, -10,   0,  10,  10 * needlessGrowth);
     await testResizer(  0,   0, -10,  10,  10, -10 * reversedGrowth);
     await testResizer(  0,   0,   0, -10,  10 * needlessGrowth,  10);
     await testResizer(  0,   0,   0,   0,   0,   0);
     await testResizer(  0,   0,   0,  10,   0, -10 * ignoredGrowth);
     await testResizer(  0,   0,  10, -10, -10 * reversedGrowth,  10);
     await testResizer(  0,   0,  10,   0, -10 * ignoredGrowth,   0);
     await testResizer(  0,   0,  10,  10, -10, -10);
+
+    /* eslint-enable no-multi-spaces */
   }
 
   const kTests = [
     { description: "Resiziers for <img>",
       innerHTML: "<img id=\"target\" src=\"green.png\">",
       mayPreserveRatio: true,
       isAbsolutePosition: false,
     },
@@ -222,17 +226,17 @@ SimpleTest.waitForFocus(async function()
       innerHTML: "<div id=\"target\" style=\"position: absolute; top: 50px; left: 50px;\">positioned</div>",
       mayPreserveRatio: false,
       isAbsolutePosition: true,
     },
   ];
 
   // Resizers for absolute positioned element and table element are available
   // only when enableAbsolutePositionEditing or enableInlineTableEditing is
-  // enabled for each.  So, let's enable them during testing resizers for 
+  // enabled for each.  So, let's enable them during testing resizers for
   // absolute positioned elements or table elements.
   await SpecialPowers.pushPrefEnv({"set": [["editor.resizing.preserve_ratio", false]]});
   for (const kTest of kTests) {
     document.execCommand("enableAbsolutePositionEditing", false, kTest.isAbsolutePosition);
     await doTest(kTest.description, false, kTest.innerHTML);
   }
   await SpecialPowers.pushPrefEnv({"set": [["editor.resizing.preserve_ratio", true]]});
   for (const kTest of kTests) {

new file mode 100644
--- /dev/null
+++ b/editor/spellchecker/tests/.eslintrc.js
@@ -0,0 +1,7 @@
+"use strict";
+
+module.exports = {
+  "extends": [
+    "plugin:mozilla/mochitest-test"
+  ]
+};