Add unit tests for configuration

tests/Makefile.am

@@ -16,4 +16,7 @@ get_devices_LDADD = $(top_builddir)/libmodule.la
 check_PROGRAMS += expand
 expand_LDADD = $(top_builddir)/libmodule.la
 
+check_PROGRAMS += config
+config_LDADD = $(top_builddir)/libmodule.la
+
 TESTS = $(check_PROGRAMS)

tests/config.c

@@ -0,0 +1,155 @@
+#undef NDEBUG
+
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <assert.h>
+
+#include "cfg.h"
+
+#define WRITE(fd, text)                                                        \
+  do {                                                                         \
+    ssize_t w = write(fd, (text), sizeof(text));                               \
+    assert(w == sizeof(text));                                                 \
+    int e = fsync(fd);                                                         \
+    assert(e == 0);                                                            \
+  } while (0)
+
+static char *abs_config_path(void) {
+  char cwd[1024];
+  char *template;
+  int err;
+
+  err = !getcwd(cwd, sizeof(cwd));
+  assert(!err);
+
+  err = asprintf(&template, "config=%.*s/test_config_XXXXXX", (int) sizeof(cwd),
+                 cwd) == -1;
+  assert(!err);
+
+  return template;
+}
+
+static void test_inherit(void) {
+  /* Testing config file inheritance: the config file provides defaults,
+   * overrides from regular argv
+   */
+
+  char *config_arg;
+  int fd;
+  cfg_t cfg;
+
+  config_arg = abs_config_path();
+
+  fd = mkstemp(config_arg + strlen("config="));
+  assert(fd != -1);
+
+  WRITE(fd, "alwaysok\nprompt=hello");
+  const char *argv[] = {
+    config_arg, "prompt=hi",
+    "debug", // So we have a log file for the test
+  };
+  cfg_init(&cfg, 0, sizeof(argv) / sizeof(*argv), argv);
+
+  unlink(config_arg + strlen("config="));
+  free(config_arg);
+  close(fd);
+
+  assert(cfg.alwaysok);
+  assert(strcmp(cfg.prompt, "hi") == 0);
+
+  cfg_free(&cfg);
+}
+
+static void test_config_abspath(void) {
+  /* Ensuring that the configuraton file path, provided via config=
+   * is absolute.
+   */
+
+  char config_arg[] = "config=test_config_XXXXXX";
+  int fd;
+  cfg_t cfg;
+
+  fd = mkstemp(config_arg + strlen("config="));
+  assert(fd != -1);
+
+  /* Same test as in test_inherit() ... */
+  WRITE(fd, "alwaysok\nprompt=hello");
+  const char *argv[] = {
+    config_arg,
+    "debug", // So we have a log file for the test
+  };
+  cfg_init(&cfg, 0, sizeof(argv) / sizeof(*argv), argv);
+
+  unlink(config_arg + strlen("config="));
+  close(fd);
+
+  /* ...but this time defaults are NOT set by the config file */
+  assert(!cfg.alwaysok);
+  assert(!cfg.prompt);
+}
+
+static void test_debug_replace(void) {
+  cfg_t cfg;
+  const char *argv[] = {
+    "debug",
+    NULL,
+    NULL,
+  };
+  char *config_arg;
+  int fd;
+
+  // Default is stderr
+  argv[0] = "debug";
+  cfg_init(&cfg, 0, 1, argv);
+  assert(cfg.debug_file == stderr);
+  cfg_free(&cfg);
+
+  // debug_file is honoured
+  argv[1] = "debug_file=syslog";
+  cfg_init(&cfg, 0, 2, argv);
+  assert(cfg.debug_file == NULL);
+  cfg_free(&cfg);
+
+  // fallback to last working debug file
+  argv[1] = "debug_file=/hopefully/this/path/does/not/exist/debug.txt";
+  cfg_init(&cfg, 0, 2, argv);
+  assert(cfg.debug_file == stderr);
+  cfg_free(&cfg);
+
+  // A valid config file
+  config_arg = abs_config_path();
+  fd = mkstemp(config_arg + strlen("config="));
+  assert(fd != -1);
+  WRITE(fd, "debug_file=stdout");
+
+  // debug_file from config is honoured
+  argv[1] = config_arg;
+  cfg_init(&cfg, 0, 2, argv);
+  assert(cfg.debug_file == stdout);
+  cfg_free(&cfg);
+
+  // debug_file from config can be overriden
+  argv[2] = "debug_file=syslog";
+  cfg_init(&cfg, 0, 3, argv);
+  assert(cfg.debug_file != stdout);
+  cfg_free(&cfg);
+
+  // Valid debug_file from config is not replaced by bogus path
+  argv[2] = "debug_file=/hopefully/this/path/does/not/exist/debug.txt";
+  cfg_init(&cfg, 0, 3, argv);
+  assert(cfg.debug_file == stdout);
+  cfg_free(&cfg);
+
+  unlink(config_arg + strlen("config="));
+  free(config_arg);
+  close(fd);
+}
+
+int main(int argc, char **argv) {
+  (void) argc, (void) argv;
+
+  test_inherit();
+  test_config_abspath();
+  test_debug_replace();
+}