diff --git a/+stdlib/+fileio/md5sum.m b/+stdlib/+fileio/md5sum.m
index 960ccce..adfdefb 100644
--- a/+stdlib/+fileio/md5sum.m
+++ b/+stdlib/+fileio/md5sum.m
@@ -9,8 +9,6 @@
 file = expanduser(file);
 assert(isfile(file), '%s not found', file)
 
-hash = string.empty;
-
 if ismac
   [stat,hash] = system("md5 -r " + file);
 elseif isunix
@@ -18,14 +16,13 @@
 elseif ispc
   [stat,hash] = system("CertUtil -hashfile " + file + " MD5");
 else
-  return
+  error("no sha256sum method for your OS")
 end
 
-if stat ~= 0
-  return
-end
+assert(stat == 0, hash)
 
 hash = regexp(hash,'^\w{32}','match','once','lineanchors');
+hash = string(hash);
 
 assert(strlength(hash)==32, 'md5 hash is 32 characters')
 
diff --git a/+stdlib/+fileio/sha256sum.m b/+stdlib/+fileio/sha256sum.m
index 7e4d954..c8956f4 100644
--- a/+stdlib/+fileio/sha256sum.m
+++ b/+stdlib/+fileio/sha256sum.m
@@ -9,8 +9,6 @@
 file = expanduser(file);
 assert(isfile(file), '%s not found', file)
 
-hash = string.empty;
-
 if ismac
   [stat,hash] = system("shasum --algorithm 256 --binary " + file);
 elseif isunix
@@ -18,14 +16,13 @@
 elseif ispc
   [stat,hash] = system("CertUtil -hashfile " + file + " SHA256");
 else
-  return
+  error("no md5sum method for your OS")
 end
 
-if stat ~= 0
-  return
-end
+assert(stat == 0, hash)
 
 hash = regexp(hash,'^\w{64}','match','once','lineanchors');
+hash = string(hash);
 
 assert(strlength(hash)==64, 'SHA256 hash is 64 characters')
 
diff --git a/+stdlib/TestFileio.m b/+stdlib/TestFileio.m
index 2e10fcd..9572001 100644
--- a/+stdlib/TestFileio.m
+++ b/+stdlib/TestFileio.m
@@ -142,6 +142,21 @@ function test_copyfile(tc)
 tc.verifyThat(fullfile(tempdir, name), IsFile)
 end
 
+function test_hash(tc)
+import matlab.unittest.constraints.IsFile
+
+fn = tempname;
+fid = fopen(fn, "w");
+tc.assumeGreaterThan(fid, 0);
+fprintf(fid, "hello");
+fclose(fid);
+tc.assumeThat(fn, IsFile)
+
+tc.verifyEqual(stdlib.fileio.md5sum(fn), "5d41402abc4b2a76b9719d911017c592")
+tc.verifyEqual(stdlib.fileio.sha256sum(fn), "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824")
+
+delete(fn)
 end
 
 end
+end
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 90fe32b..976c38a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,7 +8,8 @@ on:
 
 
 jobs:
-  linux:
+
+  matlab:
     timeout-minutes: 15
     runs-on: ${{ matrix.os }}