fix bu_file test failure by adapting our test.

test previously assumed we're running on a unix-like filesystem with distinct read/write/execute bits that are set a particular way by default.  this was both wrong for different umask settings as well as different filesystems (e.g., exfat) that are fixed-permissive (akin to immutable 777 everywhere).  thus, changed the test to force the files permissive with an bu_fchmod(777) where we can at least ensure read/write/execute are set (and we can't reliably check if unset after bu_fchmod(000) or variations thereof without knowing the FS).

also added a few more checks to make sure files exist and do not exist at the expected times.

src/libbu/tests/file.c

@@ -31,6 +31,7 @@
 #include "bu.h"
 #include "bio.h"
 
+
 int
 main(int ac, char *av[])
 {
@@ -55,35 +56,75 @@ main(int ac, char *av[])
     ret = mkdir(tdir, S_IRWXU);
 #endif
 
+    /* make sure can create an output directory */
     if (ret != 0 && !bu_file_exists(tdir, NULL)) {
-	bu_log("%s [FAIL] - could not make \"%s\" directory\n", av[0], tdir);
-	return ret;
+	bu_exit(ret, "%s [FAIL] - could not make \"%s\" directory\n", av[0], tdir);
+    }
+    if (!bu_file_directory(tdir)) {
+	bu_exit(1, "%s [FAIL] %s is not recognized as a directory\n", av[0], tdir);
     }
 
+
+    /* make sure can create files on open */
     for (int i = 1; i < file_cnt+1; i++) {
 	bu_vls_sprintf(&fname, "%s/bu_file_%d", tdir,i);
+
+	/* file does NOT exist pre-fopen() */
+	if (bu_file_exists(bu_vls_cstr(&fname), NULL)) {
+	    bu_exit(1, "%s [FAIL] test file %s already exists\n", av[0], bu_vls_cstr(&fname));
+	}
+
+	/* opening file should create it */
 	fp = fopen(bu_vls_cstr(&fname), "wb");
 	if (!fp) {
-	    bu_exit(1, "%s [FAIL] Unable to create test input file %s\n", av[0], bu_vls_cstr(&fname));
+	    bu_exit(1, "%s [FAIL] Unable to create test file %s\n", av[0], bu_vls_cstr(&fname));
 	}
+
+	/* file exists post-fopen() */
+	if (!bu_file_exists(bu_vls_cstr(&fname), NULL)) {
+	    bu_exit(1, "%s [FAIL] test file %s does not exist\n", av[0], bu_vls_cstr(&fname));
+	}
+
+	/* make file permissive.
+	 *
+	 * NOTE: some filesystems like exfat are fixed 777, so we
+	 * cannot test non-execution/non-read/non-write without taking
+	 * filesystem into consideration.  should be able to make
+	 * permissive, however, and test positive case accordingly.
+	 */
+	ret = bu_fchmod(fileno(fp), 0777);
+	if (ret) {
+	    perror("bu_fchmod");
+	    bu_exit(1, "%s [FAIL] test file %s threw an fchmod() error\n", av[0], bu_vls_cstr(&fname));
+	}
+
+	/* write something to it */
 	fprintf(fp, "%d", i);
 	fclose(fp);
+
+	/* file exists post-fclose() */
+	if (!bu_file_exists(bu_vls_cstr(&fname), NULL)) {
+	    bu_exit(1, "%s [FAIL] test file %s does not exist\n", av[0], bu_vls_cstr(&fname));
+	}
     }
 
     /* Do some tests on the files */
     for (int i = 1; i < file_cnt+1; i++) {
+
+	/* NOTE: some filesystems (e.g., exfat) are ONLY permissible
+	 * (e.g., 777), so we can only trigger on not being readable,
+	 * not writeable, not executable after running bu_fchmod(777).
+	 */
+
 	bu_vls_sprintf(&fname, "%s/bu_file_%d", tdir,i);
-	if (!bu_file_exists(bu_vls_cstr(&fname), NULL)) {
-	    bu_exit(1, "%s [FAIL] test input file %s does not exist\n", av[0], bu_vls_cstr(&fname));
-	}
 	if (!bu_file_readable(bu_vls_cstr(&fname))) {
-	    bu_exit(1, "%s [FAIL] test input file %s is not readable\n", av[0], bu_vls_cstr(&fname));
+	    bu_exit(1, "%s [FAIL] test file %s not readable after bu_fchmod(777)\n", av[0], bu_vls_cstr(&fname));
 	}
 	if (!bu_file_writable(bu_vls_cstr(&fname))) {
-	    bu_exit(1, "%s [FAIL] test input file %s is not readable\n", av[0], bu_vls_cstr(&fname));
+	    bu_exit(1, "%s [FAIL] test file %s not readable after bu_fchmod(777)\n", av[0], bu_vls_cstr(&fname));
 	}
-	if (bu_file_executable(bu_vls_cstr(&fname))) {
-	    bu_exit(1, "%s [FAIL] test input file %s is incorrectly reported to be executable\n", av[0], bu_vls_cstr(&fname));
+	if (!bu_file_executable(bu_vls_cstr(&fname))) {
+	    bu_exit(1, "%s [FAIL] test file %s not executable after bu_fchmod(777)\n", av[0], bu_vls_cstr(&fname));
 	}
     }
 
@@ -94,10 +135,6 @@ main(int ac, char *av[])
 	bu_exit(1, "%s [FAIL] test input files %s and %s are incorrectly reported to be the same file\n", av[0], bu_vls_cstr(&fname), bu_vls_cstr(&fname2));
     }
 
-    if (!bu_file_directory(tdir)) {
-	bu_exit(1, "%s [FAIL] %s is not recognized as being a directory\n", av[0], tdir);
-    }
-
     if (bu_file_directory(bu_vls_cstr(&fname))) {
 	bu_exit(1, "%s [FAIL] %s is incorrectly identified as being a directory\n", av[0], bu_vls_cstr(&fname));
     }
@@ -141,6 +178,11 @@ main(int ac, char *av[])
 	if (!bu_file_delete(bu_vls_cstr(&fname))) {
 	    bu_exit(1, "%s [FAIL] could not delete file %s\n", av[0], bu_vls_cstr(&fname));
 	}
+
+    	/* file exists post-delete */
+	if (bu_file_exists(bu_vls_cstr(&fname), NULL)) {
+	    bu_exit(1, "%s [FAIL] test file %s was deleted but still exists\n", av[0], bu_vls_cstr(&fname));
+	}
     }
 
     if (!bu_file_delete(tdir)) {