diff --git a/tests/mocha/index.html b/tests/mocha/index.html
index 00b9c4ead..6d87be36b 100644
--- a/tests/mocha/index.html
+++ b/tests/mocha/index.html
@@ -49,6 +49,7 @@
     <script src="navigation_modify_test.js"></script>
     <script src="navigation_test.js"></script>
     <script src="procedures_test.js"></script>
+    <script src="theme_test.js"></script>
     <script src="trashcan_test.js"></script>
     <script src="utils_test.js"></script>
     <script src="xml_test.js"></script>
diff --git a/tests/mocha/theme_test.js b/tests/mocha/theme_test.js
new file mode 100644
index 000000000..e27675a24
--- /dev/null
+++ b/tests/mocha/theme_test.js
@@ -0,0 +1,158 @@
+/**
+ * @license
+ * Visual Blocks Editor
+ *
+ * Copyright 2019 Google Inc.
+ * https://developers.google.com/blockly/
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @fileoverview Blockly Theme tests.
+ * @author samelh@google.com (Sam El-Husseini)
+ */
+'use strict';
+
+suite('Theme', function() {
+
+  function defineThemeTestBlocks() {
+    Blockly.defineBlocksWithJsonArray([{
+      "type": "stack_block",
+      "message0": "",
+      "previousStatement": null,
+      "nextStatement": null
+    },
+    {
+      "type": "row_block",
+      "message0": "%1",
+      "args0": [
+        {
+          "type": "input_value",
+          "name": "INPUT"
+        }
+      ],
+      "output": null
+    }]);
+  }
+
+  function undefineThemeTestBlocks() {
+    delete Blockly.Blocks['stack_block'];
+    delete Blockly.Blocks['row_block'];
+  }
+
+
+  function createBlockStyles() {
+    return {
+      "styleOne": {
+        "colourPrimary": "colour1",
+        "colourSecondary":"colour2",
+        "colourTertiary":"colour3"
+      }
+    };
+  }
+
+  function createMultipleBlockStyles() {
+    return {
+      "styleOne": {
+        "colourPrimary": "colour1",
+        "colourSecondary":"colour2",
+        "colourTertiary":"colour3"
+      },
+      "styleTwo": {
+        "colourPrimary": "colour1",
+        "colourSecondary":"colour2",
+        "colourTertiary":"colour3"
+      }
+    };
+  }
+
+  function stringifyAndCompare(val1, val2) {
+    var stringVal1 = JSON.stringify(val1);
+    var stringVal2 = JSON.stringify(val2);
+    assertEquals(stringVal1, stringVal2);
+  }
+
+  test('Set All BlockStyles', function() {
+    var theme = new Blockly.Theme(createBlockStyles());
+    stringifyAndCompare(createBlockStyles(), theme.blockStyles_);
+    theme.setAllBlockStyles(createMultipleBlockStyles());
+    stringifyAndCompare(createMultipleBlockStyles(), theme.blockStyles_);
+  });
+
+  test('Get All BlockStyles', function() {
+    var theme = new Blockly.Theme(createMultipleBlockStyles());
+    var allBlocks = theme.getAllBlockStyles();
+    stringifyAndCompare(createMultipleBlockStyles(), allBlocks);
+  });
+
+  test('Get BlockStyles', function() {
+    var theme = new Blockly.Theme(createBlockStyles());
+    var blockStyle = theme.getBlockStyle('styleOne');
+
+    stringifyAndCompare(blockStyle, createBlockStyles().styleOne);
+  });
+
+  test('Set BlockStyle Update', function() {
+    var theme = new Blockly.Theme(createBlockStyles());
+    var blockStyle = createBlockStyles();
+    blockStyle.styleOne.colourPrimary = 'somethingElse';
+
+    theme.setBlockStyle('styleOne', blockStyle.styleOne);
+
+    stringifyAndCompare(theme.blockStyles_, blockStyle);
+  });
+
+  test('Set BlockStyle Add', function() {
+    var theme = new Blockly.Theme(createBlockStyles());
+    var blockStyle = createMultipleBlockStyles();
+
+    theme.setBlockStyle('styleTwo', blockStyle.styleTwo);
+
+    stringifyAndCompare(theme.blockStyles_, blockStyle);
+  });
+
+  test('Set Theme', function() {
+    defineThemeTestBlocks();
+    var blockStyles = createBlockStyles();
+    var workspace = new Blockly.WorkspaceSvg({});
+    var blockA = workspace.newBlock('stack_block');
+
+    blockA.setStyle = function() {this.styleName_ = 'styleTwo';};
+    var callCount = 1;
+    workspace.refreshToolboxSelection = function() {
+      return ++callCount;
+    };
+    blockA.styleName_ = 'styleOne';
+
+    var stub = sinon.stub(Blockly, "getMainWorkspace").returns(workspace);
+
+    Blockly.setTheme(blockStyles);
+
+    // Checks that the theme was set correctly on Blockly namespace
+    stringifyAndCompare(Blockly.getTheme(), blockStyles);
+
+    // Checks that the setTheme function was called on the block
+    assertEquals(blockA.getStyleName(), 'styleTwo');
+
+    // check that the toolbox refreshed method was called
+    assertEquals(workspace.refreshToolboxSelection(), 3);
+
+    assertEquals(Blockly.Events.FIRE_QUEUE_.pop().element, 'theme');
+
+    undefineThemeTestBlocks();
+
+    stub.restore();
+  });
+
+});