diff --git a/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/index.js b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/index.js
new file mode 100644
index 0000000000000..c27d1c33feeb4
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/index.js
@@ -0,0 +1,35 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+
+/**
+  * Changes the values of IS_DEV to false and IS_MINIFIED to true.
+  * The above said variables are in src/mode.js file.
+  * @param {Object} babelTypes
+  */
+module.exports = function({types: t}) {
+  return {
+    visitor: {
+      VariableDeclarator(path) {
+        const {node} = path;
+        const {id, init} = node;
+        if (t.isIdentifier(id, {name: 'IS_DEV'})
+            && t.isBooleanLiteral(init, {value: true})) {
+          node.init = t.booleanLiteral(false);
+        }
+      },
+    },
+  };
+};
diff --git a/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/isdev-transform/input.js b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/isdev-transform/input.js
new file mode 100644
index 0000000000000..21f1ed57dc773
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/isdev-transform/input.js
@@ -0,0 +1,19 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+
+
+const IS_DEV = true;
+const IS_EXPANDED = false;
diff --git a/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/isdev-transform/options.json b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/isdev-transform/options.json
new file mode 100644
index 0000000000000..13f0fa59df0e1
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/isdev-transform/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-is_dev-constant-transformer"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/isdev-transform/output.js b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/isdev-transform/output.js
new file mode 100644
index 0000000000000..9319a005fcae9
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/isdev-transform/output.js
@@ -0,0 +1,17 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+const IS_DEV = false;
+const IS_EXPANDED = false;
diff --git a/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/no-transform/input.js b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/no-transform/input.js
new file mode 100644
index 0000000000000..88371a1445c78
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/no-transform/input.js
@@ -0,0 +1,20 @@
+
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+
+
+const IS_DEVELOPMENT = false;
+const IS_EXPANDED = false;
diff --git a/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/no-transform/options.json b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/no-transform/options.json
new file mode 100644
index 0000000000000..13f0fa59df0e1
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/no-transform/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-is_dev-constant-transformer"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/no-transform/output.js b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/no-transform/output.js
new file mode 100644
index 0000000000000..bf4c3530b6af0
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/fixtures/transform-assertions/no-transform/output.js
@@ -0,0 +1,17 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+const IS_DEVELOPMENT = false;
+const IS_EXPANDED = false;
diff --git a/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/index.js b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/index.js
new file mode 100644
index 0000000000000..7b6d7376a7498
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_dev-constant-transformer/test/index.js
@@ -0,0 +1,19 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+
+const runner = require('@babel/helper-plugin-test-runner').default;
+
+runner(__dirname);
diff --git a/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/index.js b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/index.js
new file mode 100644
index 0000000000000..3d9f8daa5157f
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/index.js
@@ -0,0 +1,40 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+
+/**
+  * Changes the values of IS_DEV to false and IS_MINIFIED to true.
+  * The above said variables are in src/mode.js file.
+  * @param {Object} babelTypes
+  */
+module.exports = function(babelTypes) {
+  const {types: t} = babelTypes;
+  return {
+    visitor: {
+      VariableDeclarator(path) {
+        const {id, init} = path.node;
+        if (t.isIdentifier(id, {name: 'IS_MINIFIED'})
+            && t.isBooleanLiteral(init, {value: false})) {
+          path.replaceWith(
+              t.variableDeclarator(
+                  t.identifier('IS_MINIFIED'),
+                  t.booleanLiteral(true)
+              )
+          );
+        }
+      },
+    },
+  };
+};
diff --git a/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/isminified-transform/input.js b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/isminified-transform/input.js
new file mode 100644
index 0000000000000..ff730f6e824f3
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/isminified-transform/input.js
@@ -0,0 +1,19 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+
+
+const IS_DEVELOPMENT = false;
+const IS_MINIFIED = false;
diff --git a/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/isminified-transform/options.json b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/isminified-transform/options.json
new file mode 100644
index 0000000000000..be67ebac87b6e
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/isminified-transform/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-is_minified-constant-transformer"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/isminified-transform/output.js b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/isminified-transform/output.js
new file mode 100644
index 0000000000000..7ac0ff36819f0
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/isminified-transform/output.js
@@ -0,0 +1,17 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+const IS_DEVELOPMENT = false;
+const IS_MINIFIED = true;
diff --git a/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/no-transform/input.js b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/no-transform/input.js
new file mode 100644
index 0000000000000..b42410f328d2f
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/no-transform/input.js
@@ -0,0 +1,19 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+
+
+const IS_DEVELOPMENT = false;
+const IS_EXPANDED = false;
diff --git a/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/no-transform/options.json b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/no-transform/options.json
new file mode 100644
index 0000000000000..be67ebac87b6e
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/no-transform/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-is_minified-constant-transformer"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/no-transform/output.js b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/no-transform/output.js
new file mode 100644
index 0000000000000..bf4c3530b6af0
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/fixtures/transform-assertions/no-transform/output.js
@@ -0,0 +1,17 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+const IS_DEVELOPMENT = false;
+const IS_EXPANDED = false;
diff --git a/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/index.js b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/index.js
new file mode 100644
index 0000000000000..7b6d7376a7498
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-is_minified-constant-transformer/test/index.js
@@ -0,0 +1,19 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
+ *
+ * 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.
+ */
+
+const runner = require('@babel/helper-plugin-test-runner').default;
+
+runner(__dirname);
diff --git a/build-system/build.conf.js b/build-system/build.conf.js
index 9651ae86758f8..3e039dd3fb953 100644
--- a/build-system/build.conf.js
+++ b/build-system/build.conf.js
@@ -21,10 +21,16 @@ const defaultPlugins = [
       './babel-plugins/babel-plugin-transform-html-template'),
   require.resolve(
       './babel-plugins/babel-plugin-transform-parenthesize-expression'),
+  require.resolve(
+      './babel-plugins/babel-plugin-is_minified-constant-transformer'),
 ];
 
 module.exports = {
-  plugins: (isEsmBuild, isCommonJsModule) => {
+  plugins: ({
+    isEsmBuild,
+    isCommonJsModule,
+    isForTesting,
+  }) => {
     let pluginsToApply = defaultPlugins;
     if (isEsmBuild) {
       pluginsToApply = pluginsToApply.concat([
@@ -46,6 +52,15 @@ module.exports = {
         [require.resolve('babel-plugin-transform-commonjs-es2015-modules')],
       ]);
     }
+    if (!isForTesting) {
+      pluginsToApply = pluginsToApply.concat([
+        [
+          require.resolve(
+              './babel-plugins/babel-plugin-is_dev-constant-transformer'
+          ),
+        ],
+      ]);
+    }
     return pluginsToApply;
   },
 };
diff --git a/build-system/single-pass.js b/build-system/single-pass.js
index 448b12e8a52c7..8c463d2322043 100644
--- a/build-system/single-pass.js
+++ b/build-system/single-pass.js
@@ -431,9 +431,11 @@ function transformPathsToTempDir(graph, config) {
       fs.copySync(f, `${graph.tmp}/${f}`);
     } else {
       const {code} = babel.transformFileSync(f, {
-        plugins: conf.plugins(
-            /* isEsmBuild */ config.define.indexOf('ESM_BUILD=true') !== -1,
-            /* isCommonJsModule */ isCommonJsModule(f)),
+        plugins: conf.plugins({
+          isEsmBuild: config.define.indexOf('ESM_BUILD=true') !== -1,
+          isCommonJsModule: isCommonJsModule(f),
+          isForTesting: config.define.indexOf('FORTESTING=true') !== -1,
+        }),
         retainLines: true,
       });
       fs.outputFileSync(`${graph.tmp}/${f}`, code);