bash mocking

bash-inject.bats

setup() {
  . "${BATS_TEST_DIRNAME}/bash-inject.shlib"
}

@test "should default to defining function" {
  assert_equal "$(declare -F fn)" ''

  @inject "${BATS_TEST_DIRNAME}/fn.sh"

  run echo "$(declare -f fn)"
  assert_output -p "${BATS_TEST_DIRNAME}/fn.sh"
}

@test "should not define recursive function" {
  assert_equal "$(declare -F fn)" ''

  @inject "fn"

  run echo "$(declare -f fn)"
  assert_output ''
}

@test "should use injected function" {
  assert_equal "$(declare -F fn)" ''

  function fn() {
    echo mock fn
  }

  @inject "${BATS_TEST_DIRNAME}/fn.sh"

  run echo "$(declare -f fn)"
  assert_output -p 'echo mock fn'
}

bash-inject.shlib

# shellcheck disable=SC2148

# @inject allows an executable call to be mocked out by defining a function that calls the executable by default.
# A pre-defined function of the same name will take precedence thereby allowing mocking.
# Example:
#   In sut-script.sh:
#     @inject /path/to/dependency-executable.sh
#
#     dependency-executable dependency-executable-args
#
#   In sut-script.bats:
#     function dependency-executable() {
#       assert_equal "$1" 'arg1'
#     }
#
#     run sut-script sut-script-args
function @inject() {
  executable="$1"
  shift $#

  fn="$(basename "${executable}" | sed -e 's|\..*||')"

  quot='"'
  declare -F "${fn}" >/dev/null ||
      [ "${fn}" == "${executable}" ] ||
      eval "function ${fn}() { ${executable} ${quot}\$@${quot}; }"
}

bash-mock.bats

setup() {
  . "${BATS_TEST_DIRNAME}/bash-mock.shlib"
}

@test "should use actual dependency" {
  run "${BATS_TEST_DIRNAME}/testdata/sut-script.sh"

  assert_success
  assert_line 'first-call'
  assert_line 'second-call'
}

@test "should use mock" {
  @mock dependency-executable
  function dependency-executable@0() {
    assert_equal "$1" 'first-call'

    echo 'mocked first-call'
  }
  function dependency-executable@1() {
    assert_equal "$1" 'second-call'

    echo 'mocked second-call'
  }

  run "${BATS_TEST_DIRNAME}/testdata/sut-script.sh"

  assert_success
  assert_line 'mocked first-call'
  assert_line 'mocked second-call'
}

@test "should work when mock is called in subshells" {
  @mock dependency-executable
  function dependency-executable@0() {
    assert_equal "$1" 'first-call'

    echo 'mocked first-call'
  }
  function dependency-executable@1() {
    assert_equal "$1" 'second-call'

    echo 'mocked second-call'
  }

  run "${BATS_TEST_DIRNAME}/testdata/sut-script-with-subshell-calls.sh"

  assert_success
  assert_line 'mocked first-call'
  assert_line 'mocked second-call'
}

bash-mock.shlib

# shellcheck disable=SC2148

# @mock creates a base mock function that delegates to other mock implementations.
# Example:
#   In sut-script.sh:
#     @inject dependency-executable
#
#     dependency-executable dependency-executable-args
#
#   In sut-script.bats:
#     @mock dependency-executable
#     # will be called on sut-script.sh's first call to dependency-executable
#     function dependency-executable@0() {
#       assert_equal "$1" 'first-call'
#     }
#     # will be called on sut-script.sh's second call to dependency-executable
#     function dependency-executable@1() {
#       assert_equal "$1" 'second-call'
#     }
#
#     run sut-script sut-script-args
# TODO(nyap): support each mock implementation being called a specified number of times; currently, each implementation is called only once
function @mock() {
  tmpdir="$(mktemp -d --tmpdir="${BATS_TMPDIR}")"

  name="$1"
  counter_name="${name/-/_}_counter"
  counter_filename="${tmpdir}/${counter_name}"

  echo "${counter_name}=0" >"${counter_filename}"

  quot='"'
  # since the mock can be called from sub-shells, the counter state is stored in a file
  eval "function ${name}() {
    . ${counter_filename};
    echo ${counter_name}=\$((${counter_name} + 1)) >${counter_filename};

    ${name}@\${${counter_name}} ${quot}\$@${quot};
  }"
}