diff --git a/news/no-subprocess.rst b/news/no-subprocess.rst
new file mode 100644
index 0000000..90f37de
--- /dev/null
+++ b/news/no-subprocess.rst
@@ -0,0 +1,23 @@
+**Added:**
+
+* <news item>
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* Removed subprocess calls in test functions.
diff --git a/tests/test_morphsqueeze.py b/tests/test_morphsqueeze.py
index cc741bc..a4b2d6b 100644
--- a/tests/test_morphsqueeze.py
+++ b/tests/test_morphsqueeze.py
@@ -1,9 +1,8 @@
-import subprocess
-
 import numpy as np
 import pytest
 from numpy.polynomial import Polynomial
 
+from diffpy.morph.morphapp import create_option_parser, single_morph
 from diffpy.morph.morphs.morphsqueeze import MorphSqueeze
 
 squeeze_coeffs_dic = [
@@ -119,7 +118,9 @@ def test_morphsqueeze(x_morph, x_target, squeeze_coeffs):
         ),
     ],
 )
-def test_morphsqueeze_extrapolate(user_filesystem, squeeze_coeffs, wmsg_gen):
+def test_morphsqueeze_extrapolate(
+    user_filesystem, capsys, squeeze_coeffs, wmsg_gen
+):
     x_morph = np.linspace(0, 10, 101)
     y_morph = np.sin(x_morph)
     x_target = x_morph
@@ -143,12 +144,19 @@ def test_morphsqueeze_extrapolate(user_filesystem, squeeze_coeffs, wmsg_gen):
     morph_file, target_file = create_morph_data_file(
         user_filesystem / "cwd_dir", x_morph, y_morph, x_target, y_target
     )
-    run_cmd = ["diffpy.morph"]
-    run_cmd.extend(["--squeeze=" + ",".join(map(str, coeffs))])
-    run_cmd.extend([str(morph_file), str(target_file)])
-    run_cmd.append("-n")
-    result = subprocess.run(run_cmd, capture_output=True, text=True)
-    assert expected_wmsg in result.stderr
+
+    parser = create_option_parser()
+    (opts, pargs) = parser.parse_args(
+        [
+            "--squeeze",
+            ",".join(map(str, coeffs)),
+            f"{morph_file.as_posix()}",
+            f"{target_file.as_posix()}",
+            "-n",
+        ]
+    )
+    with pytest.warns(UserWarning, match=expected_wmsg):
+        single_morph(parser, opts, pargs, stdout_flag=False)
 
 
 def create_morph_data_file(
diff --git a/tests/test_refine.py b/tests/test_refine.py
index 76263bf..2c10c19 100644
--- a/tests/test_refine.py
+++ b/tests/test_refine.py
@@ -8,6 +8,7 @@
 
 from diffpy.morph.morph_helpers.transformpdftordf import TransformXtalPDFtoRDF
 from diffpy.morph.morph_helpers.transformrdftopdf import TransformXtalRDFtoPDF
+from diffpy.morph.morphapp import create_option_parser, single_morph
 from diffpy.morph.morphs.morphchain import MorphChain
 from diffpy.morph.morphs.morphfuncx import MorphFuncx
 from diffpy.morph.morphs.morphrgrid import MorphRGrid
@@ -181,7 +182,7 @@ def stretch(x, y, stretch):
 
         assert res < err
 
-    def test_refine_grid_bad(self, user_filesystem):
+    def test_refine_grid_bad(self, user_filesystem, capsys):
         grid = numpy.arange(2)
         func = numpy.sin(grid)
         grid1, func1, grid2, func2 = grid, func, grid, func
@@ -208,9 +209,7 @@ def test_refine_grid_bad(self, user_filesystem):
         actual_error_message = str(error.value)
         assert actual_error_message == expected_error_message
 
-        # call from command line
-        import subprocess
-
+        # Test from command line
         data_dir_path = user_filesystem / "cwd_dir"
         morph_file = data_dir_path / "morph_data"
         morph_data_text = [
@@ -224,18 +223,18 @@ def test_refine_grid_bad(self, user_filesystem):
         ]
         target_data_text = "\n".join(target_data_text)
         target_file.write_text(target_data_text)
-        run_cmd = ["diffpy.morph"]
+        run_cmd = []
         for key, value in config.items():
             run_cmd.append(f"--{key}")
             run_cmd.append(f"{value}")
         run_cmd.extend([str(morph_file), str(target_file)])
         run_cmd.append("-n")
-        result = subprocess.run(run_cmd, capture_output=True, text=True)
-        expected_error_message = (
-            "diffpy.morph: error: " + expected_error_message
-        )
-        actual_error_message = result.stderr.strip()
-        assert actual_error_message == expected_error_message
+        parser = create_option_parser()
+        (opts, pargs) = parser.parse_args(run_cmd)
+        with pytest.raises(SystemExit):
+            single_morph(parser, opts, pargs, stdout_flag=False)
+        _, err = capsys.readouterr()
+        assert expected_error_message in actual_error_message
 
 
 # End of class TestRefine