Drop minitest 4 support

minitest 6 was just released, and minitest 5 was released over 12
years ago. It's unlikely there are any minitest 4 users that need
updated versions of m.

Remove BUNDLE_GEMFILE usage in test_bench.rb while here.

Author: jeremyevans

README.md

@@ -124,16 +124,7 @@ CONTRIBUTING
 
 You can run all the tests with:
 
-    bundle exec rake tests
-
-You can also run tests selectively. For minitest 4 run:
-
-    bundle exec rake test:minitest4
-
-and the ones for minitest 5 or 6 with:
-
-    bundle exec rake test:minitest
-
+    bundle exec rake test
 
 LICENSE
 =======

lib/m/frameworks.rb

@@ -16,10 +16,6 @@ def self.minitest5?
       minitest_version_major == "5"
     end
 
-    def self.minitest4?
-      minitest_version_major == "4"
-    end
-
     def self.test_unit?
       defined?(Test::Unit)
     end
@@ -33,8 +29,6 @@ def framework_runner
         Runners::Minitest6.new
       elsif minitest5?
         Runners::Minitest5.new
-      elsif minitest4?
-        Runners::Minitest4.new
       elsif test_unit?
         Runners::TestUnit.new
       else
@@ -52,10 +46,6 @@ def minitest5?
       self.class.minitest5?
     end
 
-    def minitest4?
-      self.class.minitest4?
-    end
-
     def test_unit?
       self.class.test_unit?
     end

test/bench.rb

@@ -10,27 +10,19 @@
     `bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/empty_example_test.rb 2>/dev/null`
   end
 
-  bench.report("running m on an entire file with minitest4") do
-    `BUNDLE_GEMFILE=gemfiles/minitest4.gemfile bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/minitest_4_example_test.rb 2>/dev/null`
-  end
-
   bench.report("running m on an entire file with minitest") do
-    `BUNDLE_GEMFILE=gemfiles/minitest.gemfile bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/minitest_5_or_6_example_test.rb 2>/dev/null`
+    `bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/minitest_5_or_6_example_test.rb 2>/dev/null`
   end
 
   bench.report("running m on an entire file with test-unit gem") do
-    `BUNDLE_GEMFILE=gemfiles/test_unit_gem.gemfile bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/test_unit_example_test.rb 2>/dev/null`
-  end
-
-  bench.report("running m on a specific test with minitest4") do
-    `BUNDLE_GEMFILE=gemfiles/minitest4.gemfile bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/minitest_4_example_test.rb:19 2>/dev/null`
+    `bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/test_unit_example_test.rb 2>/dev/null`
   end
 
   bench.report("running m on a specific test with minitest") do
-    `BUNDLE_GEMFILE=gemfiles/minitest.gemfile bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/minitest_5_or_6_example_test.rb:19 2>/dev/null`
+    `bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/minitest_5_or_6_example_test.rb:19 2>/dev/null`
   end
 
   bench.report("running m on a specific test with test-unit gem") do
-    `BUNDLE_GEMFILE=gemfiles/test_unit_gem.gemfile bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/test_unit_example_test.rb:15 2>/dev/null`
+    `bundle exec #{RbConfig.ruby} -Ilib ./bin/m test/examples/test_unit_example_test.rb:15 2>/dev/null`
   end
 end

test/examples/minitest_4_example_test.rb

@@ -10,9 +10,7 @@ def will_it_blend?
   end
 end
 
-TestClass = M::Frameworks.minitest4? ? MiniTest::Unit::TestCase : Minitest::Test
-
-class TestMeme < TestClass
+class TestMeme < Minitest::Test
   def setup
     @meme = Meme.new
   end

test/examples/minitest_example_test.rb

@@ -45,12 +45,8 @@ def try_loading gem
   class MTest < Test::Unit::TestCase
     include ::Testable
   end
-elsif M::Frameworks.minitest5? || M::Frameworks.minitest6?
-  class MTest < Minitest::Test
-    include ::Testable
-  end
 else
-  class MTest < MiniTest::Unit::TestCase
+  class MTest < Minitest::Test
     include ::Testable
   end
 end