Testing and debugging with GoogleTest

GoogleTest is Google’s C++ testing and mocking framework: https://google.github.io/googletest/. It even includes a Bazel example in their documentation: https://google.github.io/googletest/quickstart-bazel.html cc_test is the Bazel rule to execute such a test. Let’s add a C++ testing file that exercises the magic.c we wrote already. Here’s an example (written by Claude 3.5 Sonnet)

#include <gtest/gtest.h>
#include <unistd.h>
#include <fcntl.h>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <array>
#include <string>

#define MAX_PATH_LENGTH 256

// Test helper function to create a temporary file with content
namespace {
std::string create_test_file(const std::string& content, const std::string& extension) {
    std::array<char, MAX_PATH_LENGTH> temp_path = {};
    const char* test_tmpdir = getenv("TEST_TMPDIR");
    if (test_tmpdir == nullptr) { test_tmpdir = "/tmp"; }
    (void)std::snprintf(temp_path.data(), temp_path.size(), "%s/magic_test_XXXXXX%s", test_tmpdir, extension.c_str());
    int file_desc = mkstemps(temp_path.data(), static_cast<int>(extension.length()));
    if (file_desc == -1) {
        perror("Failed to create temp file");
        return "";
    }
    ssize_t bytes_written = write(file_desc, content.c_str(), content.length());

    if (bytes_written == -1 || static_cast<size_t>(bytes_written) != content.length()) {
        perror("Failed to write to temp file");
        close(file_desc);
        return "";
    }
    close(file_desc);
    return temp_path.data();
}
}

extern "C" {
#include <magic.h>
}

class MagicTest : public ::testing::Test {
 protected:
    magic_t magic;
    void SetUp() override {
        magic = magic_open(MAGIC_MIME_TYPE);
        ASSERT_NE(magic, nullptr) << "Failed to initialize libmagic";
        ASSERT_EQ(magic_load(magic, NULL), 0) << "Failed to load magic database";
    }
    void TearDown() override {
        if (magic != nullptr) {
            magic_close(magic);
        }
    }
};

TEST_F(MagicTest, DetectMimeType) {
    // Create a temporary text file
    const std::string content = "Hello, World!";
    std::string test_file = create_test_file(content, ".txt");
    ASSERT_FALSE(test_file.empty()) << "Failed to create test file";

    // Test MIME type detection
    const char* mime_type = magic_file(magic, test_file.c_str());
    ASSERT_NE(mime_type, nullptr) << "Failed to get MIME type";
    EXPECT_STREQ(mime_type, "text/plain") << "Unexpected MIME type";

    // Cleanup
    EXPECT_EQ(remove(test_file.c_str()), 0) << "Failed to remove test file";
}

int main(int argc, char **argv) {
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

Debugging with lldb

In order to use lldb we need to perform some setup. .bazelrc

common:lldb -c dbg --features=oso_prefix_is_pwd 
common:lldb --run_under="lldb --local-lldbinit"

.lldbinit

platform settings -w $PWD
settings set target.source-map ./ $PWD

And run the following command to go into lldb view: bazel run :magic --config=lldb

​Debugging with lldb

Debugging with lldb