test:disk_cap: improve test

Author: scivision

+stdlib/+python/disk_capacity.m

@@ -10,7 +10,6 @@
   % int64 first is for Matlab <= R2022a
 catch e
   warning(e.identifier, "disk_capacity(%s) failed: %s", p, e.message);
-  f = 0;
 end
 
 f = uint64(f);

+stdlib/+sys/disk_capacity.m

@@ -16,8 +16,6 @@
 [s, t] = system(cmd);
 if s == 0
   t = str2double(t);
-else
-  t = 0;
 end
 
 t = uint64(t);

test/TestDisk.m

@@ -47,10 +47,14 @@ function test_disk_capacity(tc, Ps, disk_capacity_fun)
 
 zero = uint64(0);
 
+dc = disk_capacity_fun(Ps);
+
+tc.verifyClass(dc, 'uint64')
+
 if stdlib.exists(Ps)
-  tc.verifyGreaterThan(disk_capacity_fun(Ps), zero)
+  tc.verifyGreaterThan(dc, zero)
 else
-  tc.verifyEqual(disk_capacity_fun(Ps), zero)
+  tc.verifyEqual(dc, zero)
 end
 end