diff --git a/pom.xml b/pom.xml
index 57e297bc9feaa94f690e79b1fd13915b38b23b38..35659617b513523fa2caf54c98f39d8b6a34106f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -75,7 +75,6 @@
     <!-- Test Dependencies -->
     <junit.version>4.12</junit.version>
     <assertj.version>1.7.0</assertj.version>
-    <mockito.version>1.9.5</mockito.version>
     <robolectric.version>3.8</robolectric.version>
   </properties>
 
@@ -195,11 +194,6 @@
         <artifactId>assertj-core</artifactId>
         <version>${assertj.version}</version>
       </dependency>
-      <dependency>
-        <groupId>org.mockito</groupId>
-        <artifactId>mockito-core</artifactId>
-        <version>${mockito.version}</version>
-      </dependency>
       <dependency>
         <groupId>com.google.guava</groupId>
         <artifactId>guava</artifactId>
diff --git a/retrofit-mock/pom.xml b/retrofit-mock/pom.xml
index 1c943c326f8c76b5577fd34a894a06702cb5f4da..570a670068e84faa28e5a9c312ded5602565294d 100644
--- a/retrofit-mock/pom.xml
+++ b/retrofit-mock/pom.xml
@@ -35,11 +35,6 @@
       <artifactId>assertj-core</artifactId>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>org.mockito</groupId>
-      <artifactId>mockito-core</artifactId>
-      <scope>test</scope>
-    </dependency>
   </dependencies>
 
   <build>
diff --git a/retrofit/pom.xml b/retrofit/pom.xml
index 16808f39938509cd3ba6857f2ae805a00cdd48fb..7eccd97d59a67d2a3b46906441b41f46cfd096e8 100644
--- a/retrofit/pom.xml
+++ b/retrofit/pom.xml
@@ -56,11 +56,6 @@
       <artifactId>assertj-core</artifactId>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>org.mockito</groupId>
-      <artifactId>mockito-core</artifactId>
-      <scope>test</scope>
-    </dependency>
     <dependency>
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>
diff --git a/retrofit/src/test/java/retrofit2/CallTest.java b/retrofit/src/test/java/retrofit2/CallTest.java
index 4f579034f5e811f2c3feda83b9a8d73c5a84107a..a99bf3646d05e75f9bd94586e406383fc27fb85a 100644
--- a/retrofit/src/test/java/retrofit2/CallTest.java
+++ b/retrofit/src/test/java/retrofit2/CallTest.java
@@ -47,8 +47,6 @@ import static okhttp3.mockwebserver.SocketPolicy.DISCONNECT_DURING_RESPONSE_BODY
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
-import static org.mockito.Mockito.spy;
-import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static retrofit2.TestingUtils.repeat;
 
 public final class CallTest {
@@ -371,11 +369,11 @@ public final class CallTest {
   }
 
   @Test public void http204SkipsConverter() throws IOException {
-    final Converter<ResponseBody, String> converter = spy(new Converter<ResponseBody, String>() {
-      @Override public String convert(ResponseBody value) throws IOException {
-        return value.string();
+    final Converter<ResponseBody, String> converter = new Converter<ResponseBody, String>() {
+      @Override public String convert(ResponseBody value) {
+        throw new AssertionError();
       }
-    });
+    };
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl(server.url("/"))
         .addConverterFactory(new ToStringConverterFactory() {
@@ -393,15 +391,14 @@ public final class CallTest {
     Response<String> response = example.getString().execute();
     assertThat(response.code()).isEqualTo(204);
     assertThat(response.body()).isNull();
-    verifyNoMoreInteractions(converter);
   }
 
   @Test public void http205SkipsConverter() throws IOException {
-    final Converter<ResponseBody, String> converter = spy(new Converter<ResponseBody, String>() {
-      @Override public String convert(ResponseBody value) throws IOException {
-        return value.string();
+    final Converter<ResponseBody, String> converter = new Converter<ResponseBody, String>() {
+      @Override public String convert(ResponseBody value) {
+        throw new AssertionError();
       }
-    });
+    };
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl(server.url("/"))
         .addConverterFactory(new ToStringConverterFactory() {
@@ -419,7 +416,6 @@ public final class CallTest {
     Response<String> response = example.getString().execute();
     assertThat(response.code()).isEqualTo(205);
     assertThat(response.body()).isNull();
-    verifyNoMoreInteractions(converter);
   }
 
   @Test public void converterBodyDoesNotLeakContentInIntermediateBuffers() throws IOException {
diff --git a/retrofit/src/test/java/retrofit2/DefaultCallAdapterFactoryTest.java b/retrofit/src/test/java/retrofit2/DefaultCallAdapterFactoryTest.java
index 9a40ca5f13f4292c03287b6f939d0abb82b0232b..e23a5d3c1aa325788141d2e6432e1957fe01872c 100644
--- a/retrofit/src/test/java/retrofit2/DefaultCallAdapterFactoryTest.java
+++ b/retrofit/src/test/java/retrofit2/DefaultCallAdapterFactoryTest.java
@@ -21,16 +21,14 @@ import java.lang.annotation.Annotation;
 import java.lang.reflect.Type;
 import java.util.List;
 import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicBoolean;
 import okhttp3.Request;
+import org.jetbrains.annotations.NotNull;
 import org.junit.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
-import static org.mockito.Matchers.any;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.spy;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.verifyNoMoreInteractions;
 
 @SuppressWarnings("unchecked")
 public final class DefaultCallAdapterFactoryTest {
@@ -39,13 +37,11 @@ public final class DefaultCallAdapterFactoryTest {
   private final Retrofit retrofit = new Retrofit.Builder()
       .baseUrl("http://localhost:1")
       .build();
-  private final Callback<String> callback = mock(Callback.class);
-  private final Executor callbackExecutor = spy(new Executor() {
-    @Override public void execute(Runnable runnable) {
-      runnable.run();
+  private final CallAdapter.Factory factory = new DefaultCallAdapterFactory(new Executor() {
+    @Override public void execute(@NotNull Runnable command) {
+      command.run();
     }
   });
-  private final CallAdapter.Factory factory = new DefaultCallAdapterFactory(callbackExecutor);
 
   @Test public void rawTypeThrows() {
     try {
@@ -74,68 +70,42 @@ public final class DefaultCallAdapterFactoryTest {
         (CallAdapter<String, Call<String>>) factory.get(returnType, NO_ANNOTATIONS, retrofit);
     final Response<String> response = Response.success("Hi");
     Call<String> call = adapter.adapt(new EmptyCall() {
-      @Override public Response<String> execute() throws IOException {
+      @Override public Response<String> execute() {
         return response;
       }
     });
     assertThat(call.execute()).isSameAs(response);
   }
 
-  @Test public void adaptedCallEnqueueUsesExecutorForSuccessCallback() {
-    Type returnType = new TypeToken<Call<String>>() {}.getType();
-    CallAdapter<String, Call<String>> adapter =
-        (CallAdapter<String, Call<String>>) factory.get(returnType, NO_ANNOTATIONS, retrofit);
-    final Response<String> response = Response.success("Hi");
-    EmptyCall originalCall = new EmptyCall() {
-      @Override public void enqueue(Callback<String> callback) {
-        callback.onResponse(this, response);
-      }
-    };
-    Call<String> call = adapter.adapt(originalCall);
-    call.enqueue(callback);
-    verify(callbackExecutor).execute(any(Runnable.class));
-    verify(callback).onResponse(call, response);
-  }
-
-  @Test public void adaptedCallEnqueueUsesExecutorForFailureCallback() {
+  @Test public void adaptedCallCloneDeepCopy() {
     Type returnType = new TypeToken<Call<String>>() {}.getType();
     CallAdapter<String, Call<String>> adapter =
         (CallAdapter<String, Call<String>>) factory.get(returnType, NO_ANNOTATIONS, retrofit);
-    final Throwable throwable = new IOException();
-    EmptyCall originalCall = new EmptyCall() {
-      @Override public void enqueue(Callback<String> callback) {
-        callback.onFailure(this, throwable);
+    final AtomicBoolean cloned = new AtomicBoolean();
+    Call<String> delegate = new EmptyCall() {
+      @Override public Call<String> clone() {
+        cloned.set(true);
+        return this;
       }
     };
-    Call<String> call = adapter.adapt(originalCall);
-    call.enqueue(callback);
-    verify(callbackExecutor).execute(any(Runnable.class));
-    verifyNoMoreInteractions(callbackExecutor);
-    verify(callback).onFailure(call, throwable);
-    verifyNoMoreInteractions(callback);
-  }
-
-  @Test public void adaptedCallCloneDeepCopy() {
-    Type returnType = new TypeToken<Call<String>>() {}.getType();
-    CallAdapter<String, Call<String>> adapter =
-        (CallAdapter<String, Call<String>>) factory.get(returnType, NO_ANNOTATIONS, retrofit);
-    Call<String> delegate = mock(Call.class);
     Call<String> call = adapter.adapt(delegate);
-    Call<String> cloned = call.clone();
-    assertThat(cloned).isNotSameAs(call);
-    verify(delegate).clone();
-    verifyNoMoreInteractions(delegate);
+    assertThat(call.clone()).isNotSameAs(call);
+    assertTrue(cloned.get());
   }
 
   @Test public void adaptedCallCancel() {
     Type returnType = new TypeToken<Call<String>>() {}.getType();
     CallAdapter<String, Call<String>> adapter =
         (CallAdapter<String, Call<String>>) factory.get(returnType, NO_ANNOTATIONS, retrofit);
-    Call<String> delegate = mock(Call.class);
+    final AtomicBoolean canceled = new AtomicBoolean();
+    Call<String> delegate = new EmptyCall() {
+      @Override public void cancel() {
+        canceled.set(true);
+      }
+    };
     Call<String> call = adapter.adapt(delegate);
     call.cancel();
-    verify(delegate).cancel();
-    verifyNoMoreInteractions(delegate);
+    assertTrue(canceled.get());
   }
 
   static class EmptyCall implements Call<String> {
diff --git a/retrofit/src/test/java/retrofit2/RetrofitTest.java b/retrofit/src/test/java/retrofit2/RetrofitTest.java
index 5608200a14f4ac3d7c4473110ca348db9e889ffc..7b7240dc6a38842861ecb775c4a14cf5b3631cc7 100644
--- a/retrofit/src/test/java/retrofit2/RetrofitTest.java
+++ b/retrofit/src/test/java/retrofit2/RetrofitTest.java
@@ -40,6 +40,7 @@ import okhttp3.RequestBody;
 import okhttp3.ResponseBody;
 import okhttp3.mockwebserver.MockResponse;
 import okhttp3.mockwebserver.MockWebServer;
+import org.jetbrains.annotations.NotNull;
 import org.junit.Rule;
 import org.junit.Test;
 import retrofit2.helpers.DelegatingCallAdapterFactory;
@@ -55,16 +56,10 @@ import static java.lang.annotation.RetentionPolicy.RUNTIME;
 import static okhttp3.mockwebserver.SocketPolicy.DISCONNECT_AT_START;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
-import static org.mockito.Matchers.any;
-import static org.mockito.Mockito.doReturn;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.spy;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.verifyNoMoreInteractions;
-import static org.mockito.Mockito.verifyZeroInteractions;
 
 public final class RetrofitTest {
   @Rule public final MockWebServer server = new MockWebServer();
@@ -147,11 +142,24 @@ public final class RetrofitTest {
   }
 
   @Test public void cloneSharesStatefulInstances() {
-    CallAdapter.Factory callAdapter = mock(CallAdapter.Factory.class);
-    Converter.Factory converter = mock(Converter.Factory.class);
+    CallAdapter.Factory callAdapter = new CallAdapter.Factory() {
+      @Nullable @Override
+      public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
+        throw new AssertionError();
+      }
+    };
+    Converter.Factory converter = new Converter.Factory() {};
     HttpUrl baseUrl = server.url("/");
-    Executor executor = mock(Executor.class);
-    okhttp3.Call.Factory callFactory = mock(okhttp3.Call.Factory.class);
+    Executor executor = new Executor() {
+      @Override public void execute(@NotNull Runnable command) {
+        command.run();
+      }
+    };
+    okhttp3.Call.Factory callFactory = new okhttp3.Call.Factory() {
+      @Override public okhttp3.Call newCall(Request request) {
+        throw new AssertionError();
+      }
+    };
 
     Retrofit one = new Retrofit.Builder()
         .addCallAdapterFactory(callAdapter)
@@ -161,8 +169,13 @@ public final class RetrofitTest {
         .callFactory(callFactory)
         .build();
 
-    CallAdapter.Factory callAdapter2 = mock(CallAdapter.Factory.class);
-    Converter.Factory converter2 = mock(Converter.Factory.class);
+    CallAdapter.Factory callAdapter2 = new CallAdapter.Factory() {
+      @Nullable @Override
+      public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
+        throw new AssertionError();
+      }
+    };
+    Converter.Factory converter2 = new Converter.Factory() {};
     Retrofit two = one.newBuilder()
         .addCallAdapterFactory(callAdapter2)
         .addConverterFactory(converter2)
@@ -753,7 +766,11 @@ public final class RetrofitTest {
   }
 
   @Test public void callFactoryPropagated() {
-    okhttp3.Call.Factory callFactory = mock(okhttp3.Call.Factory.class);
+    okhttp3.Call.Factory callFactory = new okhttp3.Call.Factory() {
+      @Override public okhttp3.Call newCall(Request request) {
+        throw new AssertionError();
+      }
+    };
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
         .callFactory(callFactory)
@@ -771,11 +788,13 @@ public final class RetrofitTest {
   }
 
   @Test public void callFactoryUsed() throws IOException {
-    okhttp3.Call.Factory callFactory = spy(new okhttp3.Call.Factory() {
+    final AtomicBoolean called = new AtomicBoolean();
+    okhttp3.Call.Factory callFactory = new okhttp3.Call.Factory() {
       @Override public okhttp3.Call newCall(Request request) {
+        called.set(true);
         return new OkHttpClient().newCall(request);
       }
-    });
+    };
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl(server.url("/"))
         .callFactory(callFactory)
@@ -785,8 +804,7 @@ public final class RetrofitTest {
 
     CallMethod service = retrofit.create(CallMethod.class);
     service.getResponseBody().execute();
-    verify(callFactory).newCall(any(Request.class));
-    verifyNoMoreInteractions(callFactory);
+    assertTrue(called.get());
   }
 
   @Test public void callFactoryReturningNullThrows() throws IOException {
@@ -855,44 +873,47 @@ public final class RetrofitTest {
   }
 
   @Test public void builtInConvertersFirstInClone() {
-    Converter<ResponseBody, Void> converter = mock(Converter.class);
-    Converter.Factory factory = mock(Converter.Factory.class);
-    Annotation[] annotations = new Annotation[0];
+    Converter.Factory factory = new Converter.Factory() {
+      @Nullable @Override
+      public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations,
+          Retrofit retrofit) {
+        throw new AssertionError("User converter factory shouldn't be called for built-in types");
+      }
+    };
 
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
         .addConverterFactory(factory)
+        .build()
+        .newBuilder() // Do a newBuilder().builder() dance to force the internal list to clone.
         .build();
 
-    doReturn(converter).when(factory).responseBodyConverter(Void.class, annotations, retrofit);
-
-    retrofit.newBuilder().build().responseBodyConverter(Void.class, annotations);
-
-    verifyZeroInteractions(factory);
+    assertNotNull(retrofit.responseBodyConverter(Void.class, new Annotation[0]));
   }
 
   @Test public void requestConverterFactoryQueried() {
-    Type type = String.class;
-    Annotation[] parameterAnnotations = new Annotation[0];
-    Annotation[] methodAnnotations = new Annotation[1];
-
-    Converter<?, RequestBody> expectedAdapter = mock(Converter.class);
-    Converter.Factory factory = mock(Converter.Factory.class);
+    final Converter<?, RequestBody> expectedAdapter = new Converter<Object, RequestBody>() {
+      @Nullable @Override public RequestBody convert(Object value) {
+        throw new AssertionError();
+      }
+    };
+    Converter.Factory factory = new Converter.Factory() {
+      @Override public Converter<?, RequestBody> requestBodyConverter(Type type,
+          Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {
+        return String.class.equals(type)
+            ? expectedAdapter
+            : null;
+      }
+    };
 
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
         .addConverterFactory(factory)
         .build();
 
-    doReturn(expectedAdapter).when(factory).requestBodyConverter(type, parameterAnnotations,
-        methodAnnotations, retrofit);
-
-    Converter<?, RequestBody> actualAdapter = retrofit.requestBodyConverter(type,
-        parameterAnnotations, methodAnnotations);
+    Converter<?, RequestBody> actualAdapter =
+        retrofit.requestBodyConverter(String.class, new Annotation[0], new Annotation[0]);
     assertThat(actualAdapter).isSameAs(expectedAdapter);
-
-    verify(factory).requestBodyConverter(type, parameterAnnotations, methodAnnotations, retrofit);
-    verifyNoMoreInteractions(factory);
   }
 
   @Test public void requestConverterFactoryNoMatchThrows() {
@@ -953,24 +974,29 @@ public final class RetrofitTest {
   }
 
   @Test public void responseConverterFactoryQueried() {
-    Type type = String.class;
-    Annotation[] annotations = new Annotation[0];
-
-    Converter<ResponseBody, ?> expectedAdapter = mock(Converter.class);
-    Converter.Factory factory = mock(Converter.Factory.class);
+    final Converter<ResponseBody, ?> expectedAdapter = new Converter<ResponseBody, Object>() {
+      @Nullable @Override public Object convert(ResponseBody value) {
+        throw new AssertionError();
+      }
+    };
+    Converter.Factory factory = new Converter.Factory() {
+      @Nullable @Override
+      public Converter<ResponseBody, ?> responseBodyConverter(Type type, Annotation[] annotations,
+          Retrofit retrofit) {
+        return String.class.equals(type)
+            ? expectedAdapter
+            : null;
+      }
+    };
 
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
         .addConverterFactory(factory)
         .build();
 
-    doReturn(expectedAdapter).when(factory).responseBodyConverter(type, annotations, retrofit);
-
-    Converter<ResponseBody, ?> actualAdapter = retrofit.responseBodyConverter(type, annotations);
+    Converter<ResponseBody, ?> actualAdapter =
+        retrofit.responseBodyConverter(String.class, new Annotation[0]);
     assertThat(actualAdapter).isSameAs(expectedAdapter);
-
-    verify(factory).responseBodyConverter(type, annotations, retrofit);
-    verifyNoMoreInteractions(factory);
   }
 
   @Test public void responseConverterFactoryNoMatchThrows() {
@@ -1031,28 +1057,33 @@ public final class RetrofitTest {
   }
 
   @Test public void stringConverterFactoryQueried() {
-    Type type = Object.class;
-    Annotation[] annotations = new Annotation[0];
-
-    Converter<?, String> expectedConverter = mock(Converter.class);
-    Converter.Factory factory = mock(Converter.Factory.class);
+    final Converter<?, String> expectedConverter = new Converter<Object, String>() {
+      @Nullable @Override public String convert(Object value) {
+        throw new AssertionError();
+      }
+    };
+    Converter.Factory factory = new Converter.Factory() {
+      @Nullable @Override
+      public Converter<?, String> stringConverter(Type type, Annotation[] annotations,
+          Retrofit retrofit) {
+        return Object.class.equals(type)
+            ? expectedConverter
+            : null;
+      }
+    };
 
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
         .addConverterFactory(factory)
         .build();
 
-    doReturn(expectedConverter).when(factory).stringConverter(type, annotations, retrofit);
-
-    Converter<?, String> actualConverter = retrofit.stringConverter(type, annotations);
+    Converter<?, String> actualConverter =
+        retrofit.stringConverter(Object.class, new Annotation[0]);
     assertThat(actualConverter).isSameAs(expectedConverter);
-
-    verify(factory).stringConverter(type, annotations, retrofit);
-    verifyNoMoreInteractions(factory);
   }
 
   @Test public void converterFactoryPropagated() {
-    Converter.Factory factory = mock(Converter.Factory.class);
+    Converter.Factory factory = new Converter.Factory() {};
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
         .addConverterFactory(factory)
@@ -1077,7 +1108,12 @@ public final class RetrofitTest {
   }
 
   @Test public void callAdapterFactoryPropagated() {
-    CallAdapter.Factory factory = mock(CallAdapter.Factory.class);
+    CallAdapter.Factory factory = new CallAdapter.Factory() {
+      @Nullable @Override
+      public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
+        throw new AssertionError();
+      }
+    };
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
         .addCallAdapterFactory(factory)
@@ -1086,38 +1122,55 @@ public final class RetrofitTest {
   }
 
   @Test public void callAdapterFactoryQueried() {
-    Type type = String.class;
-    Annotation[] annotations = new Annotation[0];
-
-    CallAdapter<?, ?> expectedAdapter = mock(CallAdapter.class);
-    CallAdapter.Factory factory = mock(CallAdapter.Factory.class);
+    final CallAdapter<?, ?> expectedAdapter = new CallAdapter<Object, Object>() {
+      @Override public Type responseType() {
+        throw new AssertionError();
+      }
+      @Override public Object adapt(Call<Object> call) {
+        throw new AssertionError();
+      }
+    };
+    CallAdapter.Factory factory = new CallAdapter.Factory() {
+      @Nullable @Override
+      public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
+        return String.class.equals(returnType)
+            ? expectedAdapter
+            : null;
+      }
+    };
 
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
         .addCallAdapterFactory(factory)
         .build();
 
-    doReturn(expectedAdapter).when(factory).get(type, annotations, retrofit);
-
-    CallAdapter<?, ?> actualAdapter = retrofit.callAdapter(type, annotations);
+    CallAdapter<?, ?> actualAdapter = retrofit.callAdapter(String.class, new Annotation[0]);
     assertThat(actualAdapter).isSameAs(expectedAdapter);
-
-    verify(factory).get(type, annotations, retrofit);
-    verifyNoMoreInteractions(factory);
   }
 
   @Test public void callAdapterFactoryQueriedCanDelegate() {
-    Type type = String.class;
-    Annotation[] annotations = new Annotation[0];
-
-    CallAdapter<?, ?> expectedAdapter = mock(CallAdapter.class);
-    CallAdapter.Factory factory2 = mock(CallAdapter.Factory.class);
-    CallAdapter.Factory factory1 = spy(new CallAdapter.Factory() {
+    final CallAdapter<?, ?> expectedAdapter = new CallAdapter<Object, Object>() {
+      @Override public Type responseType() {
+        throw new AssertionError();
+      }
+      @Override public Object adapt(Call<Object> call) {
+        throw new AssertionError();
+      }
+    };
+    CallAdapter.Factory factory2 = new CallAdapter.Factory() {
       @Override
       public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
+        return expectedAdapter;
+      }
+    };
+    final AtomicBoolean factory1called = new AtomicBoolean();
+    CallAdapter.Factory factory1 = new CallAdapter.Factory() {
+      @Override
+      public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
+        factory1called.set(true);
         return retrofit.nextCallAdapter(this, returnType, annotations);
       }
-    });
+    };
 
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
@@ -1125,35 +1178,45 @@ public final class RetrofitTest {
         .addCallAdapterFactory(factory2)
         .build();
 
-    doReturn(expectedAdapter).when(factory2).get(type, annotations, retrofit);
-
-    CallAdapter<?, ?> actualAdapter = retrofit.callAdapter(type, annotations);
+    CallAdapter<?, ?> actualAdapter = retrofit.callAdapter(String.class, new Annotation[0]);
     assertThat(actualAdapter).isSameAs(expectedAdapter);
-
-    verify(factory1).get(type, annotations, retrofit);
-    verifyNoMoreInteractions(factory1);
-    verify(factory2).get(type, annotations, retrofit);
-    verifyNoMoreInteractions(factory2);
+    assertTrue(factory1called.get());
   }
 
   @Test public void callAdapterFactoryQueriedCanDelegateTwiceWithoutRecursion() {
     Type type = String.class;
     Annotation[] annotations = new Annotation[0];
 
-    CallAdapter<?, ?> expectedAdapter = mock(CallAdapter.class);
-    CallAdapter.Factory factory3 = mock(CallAdapter.Factory.class);
-    CallAdapter.Factory factory2 = spy(new CallAdapter.Factory() {
+    final CallAdapter<?, ?> expectedAdapter = new CallAdapter<Object, Object>() {
+      @Override public Type responseType() {
+        throw new AssertionError();
+      }
+      @Override public Object adapt(Call<Object> call) {
+        throw new AssertionError();
+      }
+    };
+    CallAdapter.Factory factory3 = new CallAdapter.Factory() {
       @Override
       public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
+        return expectedAdapter;
+      }
+    };
+    final AtomicBoolean factory2called = new AtomicBoolean();
+    CallAdapter.Factory factory2 = new CallAdapter.Factory() {
+      @Override
+      public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
+        factory2called.set(true);
         return retrofit.nextCallAdapter(this, returnType, annotations);
       }
-    });
-    CallAdapter.Factory factory1 = spy(new CallAdapter.Factory() {
+    };
+    final AtomicBoolean factory1called = new AtomicBoolean();
+    CallAdapter.Factory factory1 = new CallAdapter.Factory() {
       @Override
       public CallAdapter<?, ?> get(Type returnType, Annotation[] annotations, Retrofit retrofit) {
+        factory1called.set(true);
         return retrofit.nextCallAdapter(this, returnType, annotations);
       }
-    });
+    };
 
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
@@ -1162,17 +1225,10 @@ public final class RetrofitTest {
         .addCallAdapterFactory(factory3)
         .build();
 
-    doReturn(expectedAdapter).when(factory3).get(type, annotations, retrofit);
-
     CallAdapter<?, ?> actualAdapter = retrofit.callAdapter(type, annotations);
     assertThat(actualAdapter).isSameAs(expectedAdapter);
-
-    verify(factory1).get(type, annotations, retrofit);
-    verifyNoMoreInteractions(factory1);
-    verify(factory2).get(type, annotations, retrofit);
-    verifyNoMoreInteractions(factory2);
-    verify(factory3).get(type, annotations, retrofit);
-    verifyNoMoreInteractions(factory3);
+    assertTrue(factory1called.get());
+    assertTrue(factory2called.get());
   }
 
   @Test public void callAdapterFactoryNoMatchThrows() {
@@ -1274,7 +1330,11 @@ public final class RetrofitTest {
   }
 
   @Test public void callbackExecutorPropagated() {
-    Executor executor = mock(Executor.class);
+    Executor executor = new Executor() {
+      @Override public void execute(@NotNull Runnable command) {
+        throw new AssertionError();
+      }
+    };
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl("http://example.com/")
         .callbackExecutor(executor)
@@ -1283,11 +1343,14 @@ public final class RetrofitTest {
   }
 
   @Test public void callbackExecutorUsedForSuccess() throws InterruptedException {
-    Executor executor = spy(new Executor() {
+    final CountDownLatch runnableLatch = new CountDownLatch(1);
+    final AtomicReference<Runnable> runnableRef = new AtomicReference<>();
+    Executor executor = new Executor() {
       @Override public void execute(Runnable command) {
-        command.run();
+        runnableRef.set(command);
+        runnableLatch.countDown();
       }
-    });
+    };
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl(server.url("/"))
         .callbackExecutor(executor)
@@ -1297,28 +1360,33 @@ public final class RetrofitTest {
 
     server.enqueue(new MockResponse());
 
-    final CountDownLatch latch = new CountDownLatch(1);
+    final CountDownLatch callbackLatch = new CountDownLatch(1);
     call.enqueue(new Callback<ResponseBody>() {
       @Override public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
-        latch.countDown();
+        callbackLatch.countDown();
       }
 
       @Override public void onFailure(Call<ResponseBody> call, Throwable t) {
         t.printStackTrace();
       }
     });
-    assertTrue(latch.await(2, TimeUnit.SECONDS));
 
-    verify(executor).execute(any(Runnable.class));
-    verifyNoMoreInteractions(executor);
+    assertTrue(runnableLatch.await(2, TimeUnit.SECONDS));
+    assertEquals(1, callbackLatch.getCount()); // Callback not run yet.
+
+    runnableRef.get().run();
+    assertTrue(callbackLatch.await(2, TimeUnit.SECONDS));
   }
 
   @Test public void callbackExecutorUsedForFailure() throws InterruptedException {
-    Executor executor = spy(new Executor() {
+    final CountDownLatch runnableLatch = new CountDownLatch(1);
+    final AtomicReference<Runnable> runnableRef = new AtomicReference<>();
+    Executor executor = new Executor() {
       @Override public void execute(Runnable command) {
-        command.run();
+        runnableRef.set(command);
+        runnableLatch.countDown();
       }
-    });
+    };
     Retrofit retrofit = new Retrofit.Builder()
         .baseUrl(server.url("/"))
         .callbackExecutor(executor)
@@ -1328,20 +1396,22 @@ public final class RetrofitTest {
 
     server.enqueue(new MockResponse().setSocketPolicy(DISCONNECT_AT_START));
 
-    final CountDownLatch latch = new CountDownLatch(1);
+    final CountDownLatch callbackLatch = new CountDownLatch(1);
     call.enqueue(new Callback<ResponseBody>() {
       @Override public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
         throw new AssertionError();
       }
 
       @Override public void onFailure(Call<ResponseBody> call, Throwable t) {
-        latch.countDown();
+        callbackLatch.countDown();
       }
     });
-    assertTrue(latch.await(2, TimeUnit.SECONDS));
 
-    verify(executor).execute(any(Runnable.class));
-    verifyNoMoreInteractions(executor);
+    assertTrue(runnableLatch.await(2, TimeUnit.SECONDS));
+    assertEquals(1, callbackLatch.getCount()); // Callback not run yet.
+
+    runnableRef.get().run();
+    assertTrue(callbackLatch.await(2, TimeUnit.SECONDS));
   }
 
   @Test public void skippedCallbackExecutorNotUsedForSuccess() throws InterruptedException {