bash-tap-mock

#!/bin/bash
#
# While not directly TAP-specific, being able to mock stuff
# in tests is pretty useful.
#
# If you're using bash-tap-bootstrap, then just source this
# file in your tests from the bash-tap directory found by
# the bootstrap by including this line after you've sourced
# bash-tap-bootstrap:
#
#   . "$BASH_TAP_ROOT/bash-tap-mock"
#
# If you're not using bash-tap-bootstrap then copy this file
# to your test directory and source it with:
#
#   . $(dirname $0)/bash-tap-mock
#
# It's important to note that if you're capturing the arguments
# passed to your mock function in a variable, and want that
# variable to be accessible to your tests, you must ensure that
# the mocked function is executed in the current shell and not
# a subshell.  In particular, this means you cannot use $() or
# `` to capture output of the function at the same time, as these
# invoke a subshell - the mock will happen, but any variables you
# set within your mock will only exist within the subshell.
# If you wish to capture output at the same time, you need to
# make use of the start_output_capture and finish_output_capture
# helper functons in bash-tap, or manually use file-descriptor
# redirects yourself to achieve the same effect.

bash_tap_mock_version='1.0.2'

if [ "${BASH_SOURCE[0]}" = "$0" ]; then
    # Being run directly, probably by test harness running entire dir.
    echo "1..0 # SKIP bash-tap-mock isn't a test file"
    exit 0
fi

function mock_function() {
    local original_name="$1"
    local mock_name="$2"
    local save_original_as="_btm_mocked_${original_name}"

    if [ -z $(declare -F "$save_original_as") ]; then
        _btm_copy_function "$original_name" "$save_original_as"
    fi
    _btm_copy_function "$mock_name" "$original_name"
}

function restore_mocked_function() {
    local original_name="$1"
    local save_original_as="_btm_mocked_${original_name}"

    if [ ! -z $(declare -F "$save_original_as") ]; then
        _btm_copy_function "$save_original_as" "$original_name"
        unset -f "$save_original_as"
    else
        _btm_caller_error "Can't find saved original function '$original_name' to restore"
    fi
}

function mock_command() {
    local command_name="$1"
    local mock_name="$2"

    if [ ! -z $(declare -F "$command_name") ]; then
        #  It's not actually a command, it's a function, mock that
        mock_function "$command_name" "$mock_name"
    else
        _btm_copy_function "$mock_name" "$command_name"
    fi
}

function restore_mocked_command() {
    local command_name="$1"

    local save_original_as="_btm_mocked_${command_name}"
    if [ ! -z $(declare -F "$save_original_as") ]; then
        #  Was actually a function mock not a command mock.
        restore_mocked_function "$command_name"
    else
        unset -f "$command_name" >/dev/null
    fi
}

# Copied from http://stackoverflow.com/a/1203628/870000
function _btm_copy_function() {
    declare -F $1 >/dev/null || _btm_caller_error "Can't find function '$1' to copy"
    eval "$(echo "${2}()"; declare -f ${1} | tail -n +2)"
}

#  Report an error from the POV of the first calling point outside this file
function _btm_caller_error() {
    local message="$*"

    local thisfile="${BASH_SOURCE[0]}"
    local file="$thisfile"
    local frame_num=2
    until [ "$file" != "$thisfile" ]; do
        frame=$(caller "$frame_num")
        IFS=' ' read line func file <<<"$frame"
    done

    echo "Error: $message, on line $line of $file" >&2
    exit 255
}