diff --git a/unittest/formats/test_dump_cfg.cpp b/unittest/formats/test_dump_cfg.cpp
index fb404e07b5..64930c3ac6 100644
--- a/unittest/formats/test_dump_cfg.cpp
+++ b/unittest/formats/test_dump_cfg.cpp
@@ -96,6 +96,8 @@ TEST_F(DumpCfgTest, write_dump)
     ASSERT_EQ(lines.size(), 124);
     ASSERT_THAT(lines[0], Eq("Number of particles = 32"));
     delete_file("dump_cfg0.melt.cfg");
+
+    TEST_FAILURE(".*ERROR: Unrecognized dump style 'xxx'.*", command("write_dump all xxx test.xxx"););
 }
 
 TEST_F(DumpCfgTest, unwrap_run0)
diff --git a/unittest/formats/test_file_operations.cpp b/unittest/formats/test_file_operations.cpp
index 7683f712a7..dbbad03adf 100644
--- a/unittest/formats/test_file_operations.cpp
+++ b/unittest/formats/test_file_operations.cpp
@@ -257,7 +257,7 @@ TEST_F(FileOperationsTest, write_data)
     command("pair_coeff * *");
     command("mass * 1.0");
     command("reset_timestep 333");
-    command("write_data noinit.data");
+    command("write_data noinit.data noinit");
     command("write_data nocoeff.data nocoeff");
     command("run 0 post no");
     command("write_data test.data");
@@ -283,6 +283,7 @@ TEST_F(FileOperationsTest, write_data)
 
     TEST_FAILURE(".*ERROR: Illegal write_data command.*", command("write_data"););
     TEST_FAILURE(".*ERROR: Illegal write_data command.*", command("write_data test.data xxxx"););
+    TEST_FAILURE(".*ERROR: Illegal write_data command.*", command("write_data test.data pair xx"););
     TEST_FAILURE(".*ERROR on proc 0: Cannot open data file some_crazy_dir/test.data:"
                  " No such file or directory.*",
                  command("write_data some_crazy_dir/test.data"););