diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/index.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/index.js
index bd4d21a2a265..c7b88407d590 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/index.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/index.js
@@ -14,111 +14,137 @@
  * limitations under the License.
  */
 
-function isRemovableMethod(t, node, names) {
-  if (!node || !t.isIdentifier(node)) {
-    return false;
-  }
-  return names.some(x => {
-    return t.isIdentifier(node, {name: x});
-  });
-}
-
 const typeMap = {
-  'assertElement': '!Element',
+  'assertElement': 'Element',
   'assertString': 'string',
   'assertNumber': 'number',
   'assertBoolean': 'boolean',
-  'assertArray': '!Array',
+  'assertArray': 'Array',
 };
 
-const removableDevAsserts = [
-  'assert',
-  'fine',
-  'assertElement',
-  'assertString',
-  'assertNumber',
-  'assertBoolean',
-  'assertArray',
-];
-
-const removableUserAsserts = ['fine'];
+const REMOVABLE = {
+  dev: [
+    'assert',
+    'fine',
+    'assertElement',
+    'assertString',
+    'assertNumber',
+    'assertBoolean',
+    'assertArray',
+  ],
+  user: ['fine'],
+};
 
 module.exports = function(babel) {
-  const {types: t} = babel;
+  const {types: t, template} = babel;
+
+  /**
+   * @param {!NodePath} path
+   * @param {!Array<string>} names
+   * @return {boolean}
+   */
+  function isRemovableMethod(path, names) {
+    return names.some(name => {
+      return path.isIdentifier({name});
+    });
+  }
+
+  /**
+   * @param {!NodePath} path
+   * @param {boolean} assertion
+   * @param {string|undefined} type
+   */
+  function eliminate(path, assertion, type) {
+    const argument = path.get('arguments.0');
+    if (!argument) {
+      if (assertion) {
+        throw path.buildCodeFrameError('assertion without a parameter!');
+      }
+
+      // This is to resolve right hand side usage of expression where
+      // no argument is passed in. This bare undefined value is eventually
+      // stripped by Closure Compiler.
+      path.replaceWith(t.identifier('undefined'));
+      return;
+    }
+
+    const arg = argument.node;
+    if (assertion) {
+      const evaluation = argument.evaluate();
+
+      // If we can statically evaluate the value to a falsey expression
+      if (evaluation.confident) {
+        if (type) {
+          if (typeof evaluation.value !== type) {
+            path.replaceWith(template.ast`
+              (function() {
+                throw new Error('static type assertion failure');
+              }());
+            `);
+            return;
+          }
+        } else if (!evaluation.value) {
+          path.replaceWith(template.ast`
+            (function() {
+              throw new Error('static assertion failure');
+            }());
+          `);
+          return;
+        }
+      }
+    }
+
+    path.replaceWith(t.parenthesizedExpression(arg));
+
+    if (type) {
+      // If it starts with a capital, make the type non-nullable.
+      if (/^[A-Z]/.test(type)) {
+        type = '!' + type;
+      }
+      // Add a cast annotation to fix type.
+      path.addComment('leading', `* @type {${type}} `);
+    }
+
+    const {parenthesized} = path.node.extra || {};
+    if (parenthesized) {
+      path.replaceWith(t.parenthesizedExpression(path.node));
+    }
+  }
+
   return {
     visitor: {
       CallExpression(path) {
-        const {node} = path;
-        const {callee} = node;
-        const {parenthesized} = node.extra || {};
+        const callee = path.get('callee');
+
+        if (callee.isIdentifier({name: 'devAssert'})) {
+          return eliminate(path, true, '');
+        }
 
-        const isDirectCallExpression = t.isIdentifier(callee, {
-          name: 'devAssert',
-        });
         const isMemberAndCallExpression =
-          t.isMemberExpression(callee) && t.isCallExpression(callee.object);
+          callee.isMemberExpression() &&
+          callee.get('object').isCallExpression();
 
-        if (!(isDirectCallExpression || isMemberAndCallExpression)) {
+        if (!isMemberAndCallExpression) {
           return;
         }
 
-        // `property` here is the identifier we want to evaluate such as the
-        // `devAssert` in a direct call or the `assert` in a `dev().assert()`
-        // call.
-        let property = null;
-        let args = null;
-        // `type` is left null in a direct call expression like `devAssert`
-        let type = null;
-
-        if (isDirectCallExpression) {
-          property = node.callee;
-          args = node.arguments[0];
-        } else if (isMemberAndCallExpression) {
-          property = callee.property;
-
-          const logCallee = callee.object.callee;
-          const isRemovableDevCall =
-            t.isIdentifier(logCallee, {name: 'dev'}) &&
-            isRemovableMethod(t, property, removableDevAsserts);
-
-          const isRemovableUserCall =
-            t.isIdentifier(logCallee, {name: 'user'}) &&
-            isRemovableMethod(t, property, removableUserAsserts);
-
-          if (!(isRemovableDevCall || isRemovableUserCall)) {
-            return;
-          }
-          args = path.node.arguments[0];
-          type = typeMap[property.name];
+        const logCallee = callee.get('object.callee');
+        let removable = [];
+
+        if (
+          logCallee.isIdentifier({name: 'dev'}) ||
+          logCallee.isIdentifier({name: 'user'})
+        ) {
+          removable = REMOVABLE[logCallee.node.name];
         }
 
-        if (args) {
-          if (parenthesized) {
-            path.replaceWith(t.parenthesizedExpression(args));
-            path.skip();
-            // If it is not an assert type, we won't need to do type annotation.
-            // If it has no type that we can cast to, then we also won't need to
-            // do type annotation.
-          } else if (!property.name.startsWith('assert') || !type) {
-            path.replaceWith(args);
-          } else {
-            // Special case null value argument since it's mostly used for
-            // interface methods with no implementation which will most likely
-            // get DCE'd by Closure Compiler since they are unused code methods.
-            if (args.type === 'NullLiteral') {
-              return;
-            } else {
-              path.replaceWith(t.parenthesizedExpression(args));
-              // Add a cast annotation to fix type.
-              path.addComment('leading', `* @type {${type}} `);
-            }
-          }
-        } else {
-          // This is to resolve right hand side usage of expression where
-          // no argument is passed in. This bare undefined value is eventually
-          // stripped by Closure Compiler.
-          path.replaceWith(t.identifier('undefined'));
+        const prop = callee.get('property');
+        if (!isRemovableMethod(prop, removable)) {
+          return;
         }
+
+        const method = prop.node.name;
+        eliminate(path, method.startsWith('assert'), typeMap[method]);
       },
     },
   };
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-dev-assert/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-dev-assert/input.js
index b85484887bf3..3f14b75234ca 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-dev-assert/input.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-dev-assert/input.js
@@ -15,4 +15,4 @@
  */
 user().assert(1 + 1);
 let result = user().assert(user(), 'hello', 'world');
-let result2 = user().assert();
+let result2 = user().assert(true);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-dev-assert/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-dev-assert/output.js
index b85484887bf3..3f14b75234ca 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-dev-assert/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-dev-assert/output.js
@@ -15,4 +15,4 @@
  */
 user().assert(1 + 1);
 let result = user().assert(user(), 'hello', 'world');
-let result2 = user().assert();
+let result2 = user().assert(true);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-userAssert/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-userAssert/output.js
index 783eb6768f10..154ca3b5450b 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-userAssert/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/no-transform-userAssert/output.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 userAssert(1 + 1);
-userAssert(2 + 2);
+userAssert((2 + 2));
 userAssert();
 let result = userAssert(dev(), 'hello', 'world');
 let result2 = userAssert();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/preserve-parens/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/preserve-parens/output.js
index fd193b570034..12c71af8ec96 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/preserve-parens/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/preserve-parens/output.js
@@ -15,10 +15,14 @@
  */
 
 /** @type {x} */
+
+/** @type {!Element} */
 (dev());
 
 function hello() {
   return (
+    /** @type {!Element} */
+
     /** @type {x} */
     (dev())
   );
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean-non/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean-non/input.js
new file mode 100644
index 000000000000..7668914ba7b1
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean-non/input.js
@@ -0,0 +1,16 @@
+/**
+ * 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.
+ */
+dev().assertBoolean(null);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean-non/options.json b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean-non/options.json
new file mode 100644
index 000000000000..9f7ccda8f0e7
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean-non/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-transform-amp-asserts"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean-non/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean-non/output.js
new file mode 100644
index 000000000000..2deb43744e5b
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean-non/output.js
@@ -0,0 +1,18 @@
+/**
+ * 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.
+ */
+(function () {
+  throw new Error('static type assertion failure');
+})();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean/input.js
index c2249a764890..23b258faaa86 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean/input.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean/input.js
@@ -17,4 +17,3 @@ const falsey = false;
 dev().assertBoolean(falsey);
 dev().assertBoolean(true);
 let result = dev().assertBoolean(false, 'hello', 'world');
-let result2 = dev().assertBoolean();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean/output.js
index c4973511d871..b0cbb07e0e9e 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-boolean/output.js
@@ -23,4 +23,3 @@ const falsey = false;
 let result =
 /** @type {boolean} */
 (false);
-let result2 = undefined;
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-element/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-element/input.js
index 24b4b6e067d8..60d8a5251975 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-element/input.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-element/input.js
@@ -15,4 +15,3 @@
  */
 dev().assertElement(element);
 let result = dev().assertElement(element, 'hello', 'world');
-let result2 = dev().assertElement();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-element/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-element/output.js
index 4b42976cad9c..109bfd9a52fa 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-element/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-element/output.js
@@ -19,4 +19,3 @@
 let result =
 /** @type {!Element} */
 (element);
-let result2 = undefined;
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number-non/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number-non/input.js
new file mode 100644
index 000000000000..7e78fd300345
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number-non/input.js
@@ -0,0 +1,16 @@
+/**
+ * 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.
+ */
+dev().assertNumber(null);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number-non/options.json b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number-non/options.json
new file mode 100644
index 000000000000..9f7ccda8f0e7
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number-non/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-transform-amp-asserts"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number-non/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number-non/output.js
new file mode 100644
index 000000000000..2deb43744e5b
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number-non/output.js
@@ -0,0 +1,18 @@
+/**
+ * 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.
+ */
+(function () {
+  throw new Error('static type assertion failure');
+})();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number/input.js
index bea63f0fb7b9..b22567373263 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number/input.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number/input.js
@@ -17,4 +17,4 @@ let num = 5;
 dev().assertNumber(num);
 dev().assertNumber(1 + 1);
 let result = dev().assertNumber(3, 'hello', 'world');
-let result2 = dev().assertNumber();
+dev().assertNumber(0);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number/output.js
index e3406a937bda..f7361847231c 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-number/output.js
@@ -23,4 +23,6 @@ let num = 5;
 let result =
 /** @type {number} */
 (3);
-let result2 = undefined;
+
+/** @type {number} */
+(0);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string-not-string-non/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string-not-string-non/input.js
new file mode 100644
index 000000000000..437c670e9107
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string-not-string-non/input.js
@@ -0,0 +1,16 @@
+/**
+ * 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.
+ */
+dev().assertString(null);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string-not-string-non/options.json b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string-not-string-non/options.json
new file mode 100644
index 000000000000..9f7ccda8f0e7
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string-not-string-non/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-transform-amp-asserts"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string-not-string-non/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string-not-string-non/output.js
new file mode 100644
index 000000000000..2deb43744e5b
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string-not-string-non/output.js
@@ -0,0 +1,18 @@
+/**
+ * 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.
+ */
+(function () {
+  throw new Error('static type assertion failure');
+})();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string/input.js
index 962ec3d2f7a6..7402b3c2d359 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string/input.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string/input.js
@@ -17,5 +17,4 @@ let str = 'foo';
 dev().assertString(str);
 dev().assertString('hello');
 let result = dev().assertString('world');
-let result2 = dev().assertString();
-let result3 = dev().assertString(null);
+let result2 = dev().assertString('');
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string/output.js
index 90364214d448..b6f4a187e125 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert-string/output.js
@@ -23,5 +23,6 @@ let str = 'foo';
 let result =
 /** @type {string} */
 ('world');
-let result2 = undefined;
-let result3 = dev().assertString(null);
+let result2 =
+/** @type {string} */
+('');
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert/input.js
index 1e45447ee8e0..bb509c0eab99 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert/input.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert/input.js
@@ -15,6 +15,4 @@
  */
 dev().assert(1 + 1);
 dev().assert(dev().assert(2 + 2));
-dev().assert();
 let result = dev().assert(dev(), 'hello', 'world');
-let result2 = dev().assert();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert/output.js
index c7b098fed679..6169818473b8 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-dev-assert/output.js
@@ -13,8 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-1 + 1;
-2 + 2;
-undefined;
-let result = dev();
-let result2 = undefined;
+(1 + 1);
+((2 + 2));
+let result = (dev());
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-empty-string/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-empty-string/input.js
new file mode 100644
index 000000000000..0ece38875290
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-empty-string/input.js
@@ -0,0 +1,16 @@
+/**
+ * Copyright 2019 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.
+ */
+devAssert('');
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-empty-string/options.json b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-empty-string/options.json
new file mode 100644
index 000000000000..9f7ccda8f0e7
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-empty-string/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-transform-amp-asserts"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-empty-string/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-empty-string/output.js
new file mode 100644
index 000000000000..1b23996b7162
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-empty-string/output.js
@@ -0,0 +1,18 @@
+/**
+ * Copyright 2019 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.
+ */
+(function () {
+  throw new Error('static assertion failure');
+})();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-false/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-false/input.js
new file mode 100644
index 000000000000..ed957dacf406
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-false/input.js
@@ -0,0 +1,16 @@
+/**
+ * Copyright 2019 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.
+ */
+devAssert(false);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-false/options.json b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-false/options.json
new file mode 100644
index 000000000000..9f7ccda8f0e7
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-false/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-transform-amp-asserts"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-false/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-false/output.js
new file mode 100644
index 000000000000..1b23996b7162
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-false/output.js
@@ -0,0 +1,18 @@
+/**
+ * Copyright 2019 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.
+ */
+(function () {
+  throw new Error('static assertion failure');
+})();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-null/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-null/input.js
new file mode 100644
index 000000000000..1bac650951bc
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-null/input.js
@@ -0,0 +1,16 @@
+/**
+ * Copyright 2019 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.
+ */
+devAssert(null);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-null/options.json b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-null/options.json
new file mode 100644
index 000000000000..9f7ccda8f0e7
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-null/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-transform-amp-asserts"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-null/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-null/output.js
new file mode 100644
index 000000000000..1b23996b7162
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-null/output.js
@@ -0,0 +1,18 @@
+/**
+ * Copyright 2019 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.
+ */
+(function () {
+  throw new Error('static assertion failure');
+})();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-zero/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-zero/input.js
new file mode 100644
index 000000000000..09bca5fa5ee9
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-zero/input.js
@@ -0,0 +1,16 @@
+/**
+ * Copyright 2019 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.
+ */
+devAssert(0);
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-zero/options.json b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-zero/options.json
new file mode 100644
index 000000000000..9f7ccda8f0e7
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-zero/options.json
@@ -0,0 +1,3 @@
+{
+  "plugins": ["../../../../../babel-plugin-transform-amp-asserts"]
+}
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-zero/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-zero/output.js
new file mode 100644
index 000000000000..1b23996b7162
--- /dev/null
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert-zero/output.js
@@ -0,0 +1,18 @@
+/**
+ * Copyright 2019 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.
+ */
+(function () {
+  throw new Error('static assertion failure');
+})();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert/input.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert/input.js
index cf5caa6619d5..2a55df63d337 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert/input.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert/input.js
@@ -15,6 +15,4 @@
  */
 devAssert(1 + 1);
 devAssert(dev().assert(2 + 2));
-devAssert();
 let result = devAssert(dev(), 'hello', 'world');
-let result2 = devAssert();
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert/output.js
index 3a2ac018bcdb..83995bbdc16f 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-devAssert/output.js
@@ -13,8 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-1 + 1;
-2 + 2;
-undefined;
-let result = dev();
-let result2 = undefined;
+(1 + 1);
+((2 + 2));
+let result = (dev());
diff --git a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-user-fine/output.js b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-user-fine/output.js
index 890202cf580c..e3c3190515ff 100644
--- a/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-user-fine/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-amp-asserts/test/fixtures/transform-assertions/transform-user-fine/output.js
@@ -13,6 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-1;
-let result = user();
+(1);
+let result = (user());
 let result2 = undefined;
diff --git a/build-system/babel-plugins/babel-plugin-transform-html-template/test/fixtures/transform-assertions/other-template-literals/output.js b/build-system/babel-plugins/babel-plugin-transform-html-template/test/fixtures/transform-assertions/other-template-literals/output.js
index f3e783f09c65..22f97010b0e9 100644
--- a/build-system/babel-plugins/babel-plugin-transform-html-template/test/fixtures/transform-assertions/other-template-literals/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-html-template/test/fixtures/transform-assertions/other-template-literals/output.js
@@ -23,4 +23,4 @@ function test(string) {
   return string;
 }
 
-console.log(test`string`);
\ No newline at end of file
+console.log(test`string`);
diff --git a/build-system/babel-plugins/babel-plugin-transform-log-methods/test/fixtures/transform-log-methods/one-arg-variadic/output.js b/build-system/babel-plugins/babel-plugin-transform-log-methods/test/fixtures/transform-log-methods/one-arg-variadic/output.js
index b564b5258e99..6aaa8c959331 100644
--- a/build-system/babel-plugins/babel-plugin-transform-log-methods/test/fixtures/transform-log-methods/one-arg-variadic/output.js
+++ b/build-system/babel-plugins/babel-plugin-transform-log-methods/test/fixtures/transform-log-methods/one-arg-variadic/output.js
@@ -24,4 +24,3 @@ devAssert(a + b, ["0", name]);
 userAssert(true, ["0", name]);
 user().assertElement(element, ["2", element]);
 dev().assertEnumValue(foo, bar, 'Unhandled because this argument is usually small');
-