Demonstrate mocha and minitest behavior with stubs

foo_test.rb

# ❯ ruby foo_test.rb
# Run options: --seed 44288

# # Running:

# F.

# Finished in 0.000679s, 2945.5069 runs/s, 2945.5069 assertions/s.

#   1) Failure:
# StubbyStubTest#test_foo_with_a_mock [foo.rb:20]:
# unexpected invocation: #<Foo:0x370>.foo(:b)
# satisfied expectations:
# - allowed any number of times, invoked once: #<Foo:0x370>.foo(:a)


# 2 runs, 2 assertions, 1 failures, 0 errors, 0 skips

require 'minitest/autorun'
require 'mocha/minitest'

class Foo
  def foo(param)
    "param: #{param}"
  end
end

class StubbyStubTest < Minitest::Test
  def test_foo_with_a
    assert_equal "param: a", Foo.new.foo(:a)
  end

  def test_foo_with_a_mock
    foo = Foo.new
    foo.stubs(:foo).with(:a).returns("test")

    assert_equal "test", foo.foo(:a)
    assert_equal "param: b", foo.foo(:b)
  end
end