diff --git a/tests/test_inp.py b/tests/test_inp.py
index a5d8703..07b8547 100644
--- a/tests/test_inp.py
+++ b/tests/test_inp.py
@@ -439,7 +439,7 @@ def test_invalid_number(self, surfaces):
                 number, transform, mnemonic, entries = surface
 
                 with pytest.raises(errors.MCNPSemanticError) as err:
-                    Surface.from_mcnp(f"{number} {transform} {mnemonic} {" ".join([str(entry) for entry in entries])}")
+                    Surface.from_mcnp(f"{number} {transform} {mnemonic} {' '.join([str(entry) for entry in entries])}")
 
                 assert err.value.code == errors.MCNPSemanticCodes.INVALID_SURFACE_NUMBER
 
@@ -454,7 +454,7 @@ def test_invalid_transformPeriodic(self, surfaces):
                 number, transform, mnemonic, entries = surface
 
                 with pytest.raises(errors.MCNPSemanticError) as err:
-                    Surface.from_mcnp(f"{number} {transform} {mnemonic} {" ".join([str(entry) for entry in entries])}")
+                    Surface.from_mcnp(f"{number} {transform} {mnemonic} {' '.join([str(entry) for entry in entries])}")
 
                 assert err.value.code == errors.MCNPSemanticCodes.INVALID_SURFACE_TRANSFORMPERIODIC
 
@@ -469,7 +469,7 @@ def test_invalid_mnemonic(self, surfaces):
                 number, transform, mnemonic, entries = surface
 
                 with pytest.raises(errors.MCNPSemanticError) as err:
-                    Surface.from_mcnp(f"{number} {transform} {mnemonic} {" ".join([str(entry) for entry in entries])}")
+                    Surface.from_mcnp(f"{number} {transform} {mnemonic} {' '.join([str(entry) for entry in entries])}")
 
                 assert err.value.code == errors.MCNPSemanticCodes.INVALID_SURFACE_MNEMONIC