diff --git a/test/unit/behaviors.html b/test/unit/behaviors.html
index 3051454e8d..a879c97ac6 100644
--- a/test/unit/behaviors.html
+++ b/test/unit/behaviors.html
@@ -395,6 +395,45 @@
       zot: 'zot'
     });
 
+    Polymer({
+      is: 'override-default-value',
+      behaviors: [
+        {
+          properties: {
+            foo: { value: true },
+            bar: { value: true}
+          }
+        },
+        {
+          properties: {
+            foo: { value: true },
+            bar: String,
+            zot: {value: true}
+          }
+        },
+
+      ],
+
+      properties: {
+        foo: String,
+        zot: String
+      }
+    });
+
+    Polymer({
+      is: 'property-observer-readonly',
+      behaviors: [
+        {
+          observers: ['_changed(bar)'],
+          _changed() {}
+        }
+      ],
+
+      properties: {
+        bar: {readOnly: true}
+      }
+    });
+
   });
   </script>
 
@@ -470,6 +509,18 @@
     </template>
   </test-fixture>
 
+  <test-fixture id="override-default-value">
+    <template>
+      <override-default-value></override-default-value>
+    </template>
+  </test-fixture>
+
+  <test-fixture id="property-observer-readonly">
+    <template>
+      <property-observer-readonly></property-observer-readonly>
+    </template>
+  </test-fixture>
+
 <script>
 
 suite('single behavior element', function() {
@@ -532,6 +583,19 @@
     assert.equal(el.nug, 'nug');
   });
 
+  test('behavior default values can be overridden', function() {
+    const el = fixture('override-default-value');
+    assert.notOk(el.foo);
+    assert.notOk(el.bar);
+    assert.notOk(el.zot);
+  });
+
+  test('readOnly not applied when property was previously observed', function() {
+    const el = fixture('property-observer-readonly');
+    el.bar = 5;
+    assert.equal(el.bar, 5);
+  });
+
 });
 
 suite('behavior.registered', function() {
diff --git a/test/unit/mixin-behaviors.html b/test/unit/mixin-behaviors.html
index e00218dc25..031c856ded 100644
--- a/test/unit/mixin-behaviors.html
+++ b/test/unit/mixin-behaviors.html
@@ -386,6 +386,37 @@
       ], Polymer.Element);
 
       customElements.define('before-register-observers', klass);
+
+      const Base = Polymer.mixinBehaviors([{
+        registered() {
+          this.usedExtendedProto = this.canUseExtendedProto;
+        }
+      }], Polymer.Element);
+
+      customElements.define('registered-proto', Polymer.mixinBehaviors([
+        {canUseExtendedProto: true}
+      ], Base));
+
+
+      class Base2 extends Polymer.mixinBehaviors([{
+          properties: {b1: String} }], Polymer.Element) {
+
+        static get properties() {
+          return { e1: String};
+        }
+      }
+
+      class El extends Polymer.mixinBehaviors([{
+          properties: {b2: String}}], Base2) {
+
+        static get properties() {
+          return { e2: String};
+        }
+
+      }
+
+      customElements.define('extended-observed-attributes', El);
+
     });
   </script>
 
@@ -436,6 +467,19 @@
       <behavior-registered-ext></behavior-registered-ext>
     </template>
   </test-fixture>
+
+  <test-fixture id="registered-proto">
+    <template>
+      <registered-proto></registered-proto>
+    </template>
+  </test-fixture>
+
+  <test-fixture id="extended-observed-attributes">
+    <template>
+      <extended-observed-attributes b1="b1" e1="e1" b2="b2" e2="e2"></extended-observed-attributes>
+    </template>
+  </test-fixture>
+
 <script>
 
 suite('single behavior element', function() {
@@ -507,6 +551,11 @@
     assert.equal(el.__fooChangedCalled, 1);
   });
 
+  test('registered called on class prototype when extended', function() {
+    var el = fixture('registered-proto');
+    assert.isTrue(el.usedExtendedProto);
+  });
+
 });
 
 suite('behavior lifecycle', function() {
@@ -654,6 +703,14 @@
     assert.deepEqual(el.__createdList, ['1', '2', 'sup', '3', '4', 'sub'], 'created list wrong');
   });
 
+  test('observedAttributes when extended', function() {
+    const el = fixture('extended-observed-attributes');
+    assert.equal(el.b1, 'b1');
+    assert.equal(el.e1, 'e1');
+    assert.equal(el.b2, 'b2');
+    assert.equal(el.e2, 'e2');
+  });
+
 });
 
 </script>