Currently, tests like fragment_shader_test.dart will only execute against the vulkan backend. flutter_tester lacks the ability to run against any other backend which is important when the test incorporates things like impellerc which behaves differently for each backend.

notes:

• while flutter_tester technically runs with the vulkan backend, it doesn't actually run the tests in question

  flutter/engine/src/flutter/testing/dart/fragment_shader_test.dart

  Line 46 in 1e87bd8

  if (impellerEnabled) {

  getUniformFloat(String name) fails on Vulkan #180595 will fix that