Add approval tests

mp3chop is so old that it didn't have very good tests. In the absence of
exhaustive tests, let's add a few approval tests. The expected output
files were generated using an older version of mp3chop and can be used
to show that the behaviour hasn't changed.

When we pass the mp3chop executable to our test script it is not passed
as a full path (see mesonbuild/meson#2681 )
and the current directory won't be in our path so we need to take
special action to ensure that we can run it.

approval-tests/meson.build

@@ -0,0 +1,3 @@
+approval_tests_script = find_program('run')
+test('approval-tests', approval_tests_script,
+     args: [ meson.current_source_dir(), meson.current_build_dir(), mp3chop_exe ])

approval-tests/run

@@ -0,0 +1,54 @@
+#!/bin/sh
+set -e
+
+src="$1"
+tmp="$2"
+exe="$3"
+
+# Meson will pass a relative path. We must convert it to an absolute
+# path before we change directory.
+mp3chop=$(realpath ${exe})
+
+[ -z "${src}" ] || cd "${src}"
+[ -n "${tmp}" ] || tmp=tmp
+[ -n "${mp3chop}" ] || mp3chop=mp3chop
+
+pass=0
+count=0
+check() {
+    name="$1"
+    input="$2"
+    expected="${name}.expected"
+    shift
+    shift
+    count=$((${count}+1))
+    echo "TEST ${name} using ${mp3chop}" 1>&2
+    ${mp3chop} "$@" < "${input}" > "${tmp}/${name}.out"
+    if cmp "${expected}" "${tmp}/${name}.out"; then
+	echo "PASS" 1>&2
+	rm "${tmp}/${name}.out"
+	pass=$((${pass}+1))
+    else
+	echo "FAIL" 1>&2
+    fi
+    echo 1>&2
+}
+
+check pass-through cbr-jstereo-32-48000.mp3
+
+check strip-id3v1 cbr-jstereo-32-48000.mp3 --strip-id3=1
+check strip-id3v2 cbr-jstereo-32-48000.mp3 --strip-id3=2
+check strip-id3 cbr-jstereo-32-48000.mp3 --strip-id3=1 --strip-id3=2
+
+dd if=/dev/zero of=${tmp}/1Mzero bs=1024 count=1024
+check no-frames ${tmp}/1Mzero
+
+cat ${tmp}/1Mzero cbr-jstereo-32-48000.mp3 > ${tmp}/leading-zeros.mp3
+cat cbr-jstereo-32-48000.mp3 ${tmp}/1Mzero > ${tmp}/trailing-zeros.mp3
+
+check leading-zeros ${tmp}/leading-zeros.mp3
+check trailing-zeros ${tmp}/trailing-zeros.mp3
+
+check beginning cbr-jstereo-32-48000.mp3 --end=20:0.0
+check end cbr-jstereo-32-48000.mp3 --begin=10:0.0
+check middle cbr-jstereo-32-48000.mp3 --begin=5:0.0 --end=25:0.0

meson.build

@@ -42,9 +42,9 @@ sources = [ 'header.cpp',
 
 libchop = static_library('chop', sources)
 
-executable('mp3chop', 'main.cpp',
-	   link_with: libchop,
-	   install: true)
+mp3chop_exe = executable('mp3chop', 'main.cpp',
+			 link_with: libchop,
+			 install: true)
 
 catch2 = subproject('catch2', required: false)
 if catch2.found()
@@ -67,4 +67,6 @@ if catch2.found()
   test('output_buffer_test', output_buffer_test)
 endif
 
+subdir('approval-tests')
+
 install_man('mp3chop.1')