tests: add at parser basic test app

tests/at/Makefile

+include ../Makefile.tests_common
+
+USEMODULE += shell
+USEMODULE += at
+
+include $(RIOTBASE)/Makefile.include

tests/at/main.c

+/*
+ * Copyright (C) 2018 OTA keys S.A.
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup tests
+ * @{
+ *
+ * @file
+ * @brief    AT module test application
+ *
+ * @author   Vincent Dupont <vincent@otakeys.com>
+ *
+ * @}
+ */
+
+#include "at.h"
+#include "shell.h"
+#include "timex.h"
+
+static at_dev_t at_dev;
+static char buf[256];
+static char resp[1024];
+
+#ifndef UART_AT
+#define UART_AT     UART_DEV(1)
+#endif
+
+#ifndef BAUDRATE_AT
+#define BAUDRATE_AT 115200
+#endif
+
+static int init(int argc, char **argv)
+{
+    (void)argc;
+    (void)argv;
+
+    at_dev_init(&at_dev, UART_AT, BAUDRATE_AT, buf, sizeof(buf));
+
+    return 0;
+}
+
+static int send(int argc, char **argv)
+{
+    if (argc < 2) {
+        puts("Please enter a command");
+        return 1;
+    }
+
+    if (at_send_cmd_get_resp(&at_dev, argv[1], resp, sizeof(resp), 10 * US_PER_SEC) > 0) {
+        puts("Response:");
+        puts(resp);
+    }
+    else {
+        puts("Error");
+    }
+
+    return 0;
+}
+
+static int drain(int argc, char **argv)
+{
+    (void)argc;
+    (void)argv;
+
+    at_drain(&at_dev);
+
+    return 0;
+}
+
+static const shell_command_t shell_commands[] = {
+    { "init", "Initialize AT device", init },
+    { "send", "Send a command and wait response", send },
+    { "drain", "Drain AT device", drain },
+    { NULL, NULL, NULL },
+};
+
+int main(void)
+{
+    puts("AT command test app");
+
+    /* run the shell */
+    char line_buf[SHELL_DEFAULT_BUFSIZE];
+    shell_run(shell_commands, line_buf, SHELL_DEFAULT_BUFSIZE);
+    return 0;
+}