diff --git a/lib/6to5/types/index.js b/lib/6to5/types/index.js
index 9956aff41b..b3e7434bb5 100644
--- a/lib/6to5/types/index.js
+++ b/lib/6to5/types/index.js
@@ -64,7 +64,14 @@ _.each(t.FLIPPED_ALIAS_KEYS, function (types, type) {
   addAssert(type, is);
 });
 
-//
+/*
+ * Shallowly checks to see if the passed `node` will evaluate to a
+ * falsy. This is if `node` is a `Literal` and `value` is falsy or
+ * `node` is an `Identifier` with a name of `undefiend`.
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
 
 t.isFalsyExpression = function (node) {
   if (t.isLiteral(node)) {
@@ -75,7 +82,14 @@ t.isFalsyExpression = function (node) {
   return false;
 };
 
-//
+/**
+ * Turn an array of statement `nodes` into a `SequenceExpression`.
+ *
+ * Variable declarations are turned into simple assignments and their
+ * declarations hoisted to the top of the current scope.
+ *
+ * Expression statements are just resolved to their standard expression.
+ */
 
 t.toSequenceExpression = function (nodes, scope) {
   var exprs = [];
@@ -116,7 +130,14 @@ t.shallowEqual = function (actual, expected) {
   return same;
 };
 
-//
+/**
+ * Description
+ *
+ * @param {Object} member
+ * @param {Object} append
+ * @param {Boolean} [computed]
+ * @returns {Object} member
+ */
 
 t.appendToMemberExpression = function (member, append, computed) {
   member.object   = t.memberExpression(member.object, member.property, member.computed);
@@ -125,12 +146,25 @@ t.appendToMemberExpression = function (member, append, computed) {
   return member;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} member
+ * @param {Object} append
+ * @returns {Object} member
+ */
+
 t.prependToMemberExpression = function (member, append) {
   member.object = t.memberExpression(append, member.object);
   return member;
 };
 
-//
+/*
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
 
 t.isDynamic = function (node) {
   if (t.isExpressionStatement(node)) {
@@ -144,6 +178,14 @@ t.isDynamic = function (node) {
   }
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Object} parent
+ * @returns {Boolean}
+ */
+
 t.isReferenced = function (node, parent) {
   // we're a property key and we aren't computed so we aren't referenced
   if (t.isProperty(parent) && parent.key === node && !parent.computed) return false;
@@ -165,11 +207,23 @@ t.isReferenced = function (node, parent) {
   return false;
 };
 
+/**
+ * Description
+ *
+ * @param {String} name
+ * @returns {Boolean}
+ */
+
 t.isValidIdentifier = function (name) {
   return _.isString(name) && esutils.keyword.isIdentifierName(name) && !esutils.keyword.isKeywordES6(name, true);
 };
 
-//
+/*
+ * Description
+ *
+ * @param {String} name
+ * @returns {String}
+ */
 
 t.toIdentifier = function (name) {
   if (t.isIdentifier(name)) return name.name;
@@ -191,11 +245,26 @@ t.toIdentifier = function (name) {
   return name || '_';
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {String} key
+ */
+
 t.ensureBlock = function (node, key) {
   key = key || "body";
   node[key] = t.toBlock(node[key], node);
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Boolean} [ignore]
+ * @returns {Object|Boolean}
+ */
+
 t.toStatement = function (node, ignore) {
   if (t.isStatement(node)) {
     return node;
@@ -229,6 +298,14 @@ t.toStatement = function (node, ignore) {
   return node;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Object} parent
+ * @returns {Object}
+ */
+
 t.toBlock = function (node, parent) {
   if (t.isBlockStatement(node)) {
     return node;
@@ -249,7 +326,14 @@ t.toBlock = function (node, parent) {
   return t.blockStatement(node);
 };
 
-//
+/*
+ * Description
+ *
+ * @param {Object} parent
+ * @param {File} file
+ * @param {Scope} scope
+ * @returns {Object}
+ */
 
 t.getUid = function (parent, file, scope) {
   var node = parent;
@@ -294,6 +378,15 @@ t.getUid = function (parent, file, scope) {
   return file.generateUidIdentifier(id, scope);
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Boolean} [map]
+ * @param {Array} [ignoreTypes]
+ * @returns {Array|Object}
+ */
+
 t.getIds = function (node, map, ignoreTypes) {
   ignoreTypes = ignoreTypes || [];
 
@@ -344,12 +437,24 @@ t.getIds.arrays = {
   ObjectPattern: ["properties"]
 };
 
-//
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
 
 t.isLet = function (node) {
   return t.isVariableDeclaration(node) && (node.kind !== "var" || node._let);
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
+
 t.isVar = function (node) {
   return t.isVariableDeclaration(node, { kind: "var" }) && !node._let;
 };
@@ -358,6 +463,13 @@ t.isVar = function (node) {
 
 t.COMMENT_KEYS = ["leadingComments", "trailingComments"];
 
+/**
+ * Description
+ *
+ * @param {Object} child
+ * @returns {Object} child
+ */
+
 t.removeComments = function (child) {
   _.each(t.COMMENT_KEYS, function (key) {
     delete child[key];
@@ -365,6 +477,14 @@ t.removeComments = function (child) {
   return child;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} child
+ * @param {Object} parent
+ * @returns {Object} child
+ */
+
 t.inheritsComments = function (child, parent) {
   _.each(t.COMMENT_KEYS, function (key) {
     child[key]  = _.uniq(_.compact([].concat(child[key], parent[key])));
@@ -372,7 +492,13 @@ t.inheritsComments = function (child, parent) {
   return child;
 };
 
-//
+/**
+ * Description
+ *
+ * @param {Object} child
+ * @param {Object} parent
+ * @returns {Object} child
+ */
 
 t.inherits = function (child, parent) {
   child.loc   = parent.loc;
@@ -383,10 +509,24 @@ t.inherits = function (child, parent) {
   return child;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} specifier
+ * @returns {String}
+ */
+
 t.getSpecifierName = function (specifier) {
   return specifier.name || specifier.id;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} specifier
+ * @returns {Boolean}
+ */
+
 t.isSpecifierDefault = function (specifier) {
   return t.isIdentifier(specifier.id) && specifier.id.name === "default";
 };
diff --git a/test/types.js b/test/types.js
new file mode 100644
index 0000000000..8a00081e68
--- /dev/null
+++ b/test/types.js
@@ -0,0 +1,55 @@
+var assert = require("assert");
+var t      = require("../lib/6to5/types");
+
+suite("types", function () {
+  test("isFalsyExpression", function () {
+    assert.ok(t.isFalsyExpression(t.literal("")));
+    assert.ok(t.isFalsyExpression(t.literal(null)));
+    assert.ok(t.isFalsyExpression(t.literal(0)));
+    assert.ok(t.isFalsyExpression(t.identifier("undefined")));
+
+    assert.ok(!t.isFalsyExpression(t.literal("foobar")));
+    assert.ok(!t.isFalsyExpression(t.literal(5)));
+    assert.ok(!t.isFalsyExpression(t.identifier("foobar")));
+  });
+
+  test("toSequenceExpression");
+
+  test("shallowEqual");
+
+  test("appendToMemberExpression");
+
+  test("prependToMemberExpression");
+
+  test("isDynamic");
+
+  test("isReferenced");
+
+  test("isValidIdentifier");
+
+  test("toIdentifier");
+
+  test("ensureBlock");
+
+  test("toStatement");
+
+  test("toBlock");
+
+  test("getUid");
+
+  test("getIds");
+
+  test("isLet");
+
+  test("isVar");
+
+  test("removeComments");
+
+  test("inheritsComments");
+
+  test("inherits");
+
+  test("getSpecifierName");
+
+  test("isSpecifierDefault");
+});