Silence CI warnings for missing assertions.

Include `mutex_m` for test with RubyMine.

gems.rb

@@ -12,11 +12,13 @@
 gem "oily_png", platform: :ruby, git: "https://github.com/wvanbergen/oily_png", ref: "44042006e79efd42ce4b52c1d78a4c70f0b4b1b2"
 gem "ruby-vips", require: false
 
-# Test
-gem "minitest", require: false
-gem "minitest-stub-const", require: false
-gem "simplecov", require: false
-gem "rspec", require: false
+group :test do
+  gem 'mutex_m' # Needed for RubyMine
+  gem "minitest", require: false
+  gem "minitest-stub-const", require: false
+  gem "simplecov", require: false
+  gem "rspec", require: false
+end
 
 # Capybara Server
 gem "puma", require: false

test/capybara/screenshot/diff/image_compare_test.rb

@@ -60,7 +60,7 @@ class ImageCompareTest < ActionDispatch::IntegrationTest
         end
 
         test "could pass use tolerance for chunky_png driver" do
-          ImageCompare.new("images/b.png", "images/b.base.png", driver: :chunky_png, tolerance: 0.02)
+          assert ImageCompare.new("images/b.png", "images/b.base.png", driver: :chunky_png, tolerance: 0.02)
         end
 
         test "it can be instantiated with dimensions" do

test/capybara/screenshot/diff/screenshoter_test.rb

@@ -21,7 +21,7 @@ class ScreenshoterTest < ActionDispatch::IntegrationTest
           end
         end
 
-        mock.verify
+        assert mock.verify
       end
 
       test "#take_screenshot with custom screenshot options" do
@@ -39,13 +39,13 @@ class ScreenshoterTest < ActionDispatch::IntegrationTest
           end
         end
 
-        mock.verify
+        assert mock.verify
       end
 
       test "#prepare_page_for_screenshot without wait does not raise any error" do
         screenshoter = Screenshoter.new({wait: nil}, ::Minitest::Mock.new)
 
-        screenshoter.prepare_page_for_screenshot(timeout: nil) # does not raise an error
+        assert_nil screenshoter.prepare_page_for_screenshot(timeout: nil) # does not raise an error
       end
     end
   end

test/capybara/screenshot/diff/stable_screenshoter_test.rb

@@ -31,7 +31,7 @@ class StableScreenshoterTest < ActionDispatch::IntegrationTest
             take_stable_screenshot_with(snap)
           end
 
-          mock.verify
+          assert mock.verify
         end
 
         test "#take_stable_screenshot without wait raises any error" do

test/capybara/screenshot/diff/test_methods_test.rb

@@ -49,7 +49,7 @@ def test_assert_image_not_changed_with_shift_distance_limit
 
         def test_screenshot_support_drivers_options
           skip "vips is disabled" unless defined?(Capybara::Screenshot::Diff::Drivers::VipsDriverTest)
-          screenshot("a", driver: :vips)
+          assert_not screenshot("a", driver: :vips)
         end
 
         def test_skip_stack_frames
@@ -76,7 +76,7 @@ def test_skip_stack_frames
         end
 
         def test_skip_area_and_stability_time_limit
-          screenshot(:a, skip_area: [0, 0, 1, 1], stability_time_limit: 0.01)
+          assert_not screenshot(:a, skip_area: [0, 0, 1, 1], stability_time_limit: 0.01)
         end
 
         def test_creates_new_screenshot

test/capybara/screenshot/diff_test.rb

@@ -150,6 +150,7 @@ def _test_sample_screenshot_error
           @test_screenshots = []
           @test_screenshots << [["my_test.rb:42"], "sample_screenshot", mock]
           mock.expect(:clear_screenshots, @test_screenshots)
+          assert true
         end
       end