flutter/dev/manual_tests/test/mock_image_http.dart

import 'dart:async';
import 'dart:io';

import 'package:mockito/mockito.dart';

import '../../../packages/flutter/test/painting/image_data.dart';

// Returns a mock HTTP client that responds with an image to all requests.
MockHttpClient createMockImageHttpClient(SecurityContext _) {
  final MockHttpClient client = new MockHttpClient();
  final MockHttpClientRequest request = new MockHttpClientRequest();
  final MockHttpClientResponse response = new MockHttpClientResponse();
  final MockHttpHeaders headers = new MockHttpHeaders();
  when(client.getUrl(any)).thenAnswer((_) => new Future<HttpClientRequest>.value(request));
  when(request.headers).thenReturn(headers);
  when(request.close()).thenAnswer((_) => new Future<HttpClientResponse>.value(response));
  when(response.contentLength).thenReturn(kTransparentImage.length);
  when(response.statusCode).thenReturn(HttpStatus.ok);
  when(response.listen(any)).thenAnswer((Invocation invocation) {
    final void Function(List<int>) onData = invocation.positionalArguments[0];
    final void Function() onDone = invocation.namedArguments[#onDone];
    final void Function(Object, [StackTrace]) onError = invocation.namedArguments[#onError];
    final bool cancelOnError = invocation.namedArguments[#cancelOnError];
    return new Stream<List<int>>.fromIterable(<List<int>>[kTransparentImage]).listen(onData, onDone: onDone, onError: onError, cancelOnError: cancelOnError);
  });
  return client;
}

class MockHttpClient extends Mock implements HttpClient {}

class MockHttpClientRequest extends Mock implements HttpClientRequest {}

class MockHttpClientResponse extends Mock implements HttpClientResponse {}

class MockHttpHeaders extends Mock implements HttpHeaders {}