How to test if value was assigned to struct?

I have the following unit test:

void testFileMapNoDirPath() {
    int argc = 3;
    char* argv[3];

    int idx = 0;
    argv[idx] = "rzsharp.exe";
    argv[++idx] = "f";
    argv[++idx] = "test.rz";

    FileMap fmap = getFileMap(argc, argv);
    int hasDir = hasDirectory(&fmap);

    if (hasDir) {
        printf("%%TEST_FAILED%% time=0 testname=testFileMapNoDirPath (testfilemap) message=fmap.dirPath has a value\n");
    }
}

...which tests the following function:

int hasDirectory(FileMap *fmap){
    return fmap->dirPath != '\0';
}

...getFileMap parses argument switches as they would be passed in from main:

FileMap getFileMap(int argc, char** argv) {
    int i;
    char* fileName = "\0";
    char* dirPath = "\0";

    for (i = 1; i < argc; i++) {
        if (strcmp(argv[i], "-d") == 0) {
            dirPath = argv[++i];
            printf("found directory: %s\n", dirPath);
        }
        else if (strcmp(argv[i], "f") == 0) {
            fileName = argv[++i];
            printf("found file: %s\n", fileName);
        }
    }
    FileMap fMap = {.fileName = fileName, .dirPath = dirPath};
    return fMap;
}

...and FileMap:

typedef struct filemap {
   const char* dirPath[128];
   const char* fileName[32];

} FileMap;

The test is supposed to be able to tell me if a directory path was provided. How can I test if dirPath has a value?