diff --git a/tests/spec/fs.fsync.spec.js b/tests/spec/fs.fsync.spec.js
index 6c218770..ce68f024 100644
--- a/tests/spec/fs.fsync.spec.js
+++ b/tests/spec/fs.fsync.spec.js
@@ -12,16 +12,18 @@ describe('fs.fsync', function() {
 
   it('should return error when fd is not a number', function(done) {
     var fs = util.fs();
-    fs.fsync('1', function(error) {
+    fs.fsync('notAnInteger', function(error) {
       expect(error).to.exist;
       expect(error.code).to.equal('EINVAL');
       done();
     });
   });
 
-  it('should return error when fd is invalid', function(done) {
-    var fs = util.fs();
-    fs.fsync(1, function(error) {
+  it('should return an error if file descriptor is negative', function(done) {
+    let fs = util.fs();
+
+    // File descriptor should be a non-negative number
+    fs.fsync(-1, function(error) {
       expect(error).to.exist;
       expect(error.code).to.equal('EBADF');
       done();
diff --git a/tests/spec/fs.ftruncate.spec.js b/tests/spec/fs.ftruncate.spec.js
index 9f6726dd..7940561f 100644
--- a/tests/spec/fs.ftruncate.spec.js
+++ b/tests/spec/fs.ftruncate.spec.js
@@ -10,6 +10,27 @@ describe('fs.ftruncate', function() {
     expect(fs.ftruncate).to.be.a('function');
   });
 
+  it('should return an error if length is not an integer', function(done) {
+    let fs = util.fs();
+    let contents = 'This is a file.';
+
+    fs.writeFile('/myfile', contents, function(error) {
+      if(error) throw error;
+
+      fs.open('/myfile', 'w', function(err, fd) {
+
+        fs.ftruncate(fd, 'notAnInteger', function(error) {
+          expect(error).to.exist;
+          expect(error.code).to.equal('EINVAL');
+          done();
+        });
+
+        // Close file descriptor when done
+        fs.close(fd);
+      });
+    });
+  });
+
   it('should return an error if length is negative', function(done) {
     let fs = util.fs();
     let contents = 'This is a file.';