Meta+Tests: Allow running FLAC spec tests

The FLAC "spec tests", or rather the test suite by xiph that exercises
weird FLAC features and edge cases, can be found at
https://github.com/ietf-wg-cellar/flac-test-files and is a good
challenge for our FLAC decoder to become more spec compliant. Running
these tests is similar to LibWasm spec tests, you need to pass
INCLUDE_FLAC_SPEC_TESTS to CMake.

As of integrating these tests, 23 out of 63 fail. :yakplus:

2 files changed, 68 insertions, 0 deletions

diff --git a/Tests/LibAudio/CMakeLists.txt b/Tests/LibAudio/CMakeLists.txt
new file mode 100644
index 0000000000..5e70e6c524
--- /dev/null
+++ b/Tests/LibAudio/CMakeLists.txt
@@ -0,0 +1,9 @@
+set(TEST_SOURCES
+    TestFLACSpec.cpp
+)
+
+foreach(source IN LISTS TEST_SOURCES)
+    serenity_test("${source}" LibAudio LIBS LibAudio)
+endforeach()
+
+install(DIRECTORY ${FLAC_SPEC_TEST_PATH} DESTINATION usr/Tests/LibAudio)
diff --git a/Tests/LibAudio/TestFLACSpec.cpp b/Tests/LibAudio/TestFLACSpec.cpp
new file mode 100644
index 0000000000..23a040d1e1
--- /dev/null
+++ b/Tests/LibAudio/TestFLACSpec.cpp
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2022, kleines Filmröllchen <filmroellchen@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/LexicalPath.h>
+#include <AK/Types.h>
+#include <LibAudio/FlacLoader.h>
+#include <LibCore/DirIterator.h>
+#include <LibCore/Stream.h>
+#include <LibTest/TestCase.h>
+
+struct FlacTest : Test::TestCase {
+    FlacTest(LexicalPath path)
+        : Test::TestCase(
+            String::formatted("flac_spec_test_{}", path.basename()), [this]() { run(); }, false)
+        , m_path(std::move(path))
+    {
+    }
+
+    void run() const
+    {
+        auto loader = Audio::FlacLoaderPlugin { m_path.string() };
+        if (auto result = loader.initialize(); result.is_error()) {
+            FAIL(String::formatted("{} (at {})", result.error().description, result.error().index));
+            return;
+        }
+
+        while (true) {
+            auto maybe_samples = loader.get_more_samples(2 * MiB);
+            if (maybe_samples.is_error()) {
+                FAIL(String::formatted("{} (at {})", maybe_samples.error().description, maybe_samples.error().index));
+                return;
+            }
+            if (maybe_samples.value().is_empty())
+                return;
+        }
+    }
+
+    LexicalPath m_path;
+};
+
+struct DiscoverFLACTestsHack {
+    DiscoverFLACTestsHack()
+    {
+        // FIXME: Also run (our own) tests in this directory.
+        auto test_iterator = Core::DirIterator { "./SpecTests", Core::DirIterator::Flags::SkipParentAndBaseDir };
+
+        while (test_iterator.has_next()) {
+            auto file = LexicalPath { test_iterator.next_full_path() };
+            if (file.extension() == "flac"sv) {
+                Test::add_test_case_to_suite(make_ref_counted<FlacTest>(move(file)));
+            }
+        }
+    }
+};
+// Hack taken from TEST_CASE; the above constructor will run as part of global initialization before the tests are actually executed
+static struct DiscoverFLACTestsHack hack;