rearrange tests and make more robust

test/fixtures/util.cpp

@@ -0,0 +1,35 @@
+#include "util.hpp"
+
+#include <csignal>
+
+namespace mbgl {
+namespace test {
+
+pid_t startServer(const char *executable) {
+    const std::string parent_pid = std::to_string(getpid());
+    pid_t pid = fork();
+    if (pid < 0) {
+        throw std::runtime_error("Cannot create server process");
+    } else if (pid == 0) {
+        char *args[] = { const_cast<char *>(executable),
+                         const_cast<char *>(parent_pid.c_str()),
+                         nullptr };
+        int ret = execv(executable, args);
+        // This call should not return. In case execve failed, we exit anyway.
+        if (ret < 0) {
+            fprintf(stderr, "Failed to start server: %s\n", strerror(errno));
+        }
+        exit(0);
+    } else {
+        // Wait until the server process sends SIGCONT.
+        raise(SIGSTOP);
+    }
+    return pid;
+}
+
+void stopServer(pid_t pid) {
+    kill(pid, SIGTERM);
+}
+
+}
+}