diff --git a/Makefile b/Makefile
index 8e49539..0f13f91 100644
--- a/Makefile
+++ b/Makefile
@@ -35,7 +35,7 @@ formatting: codestyle
 #* Linting
 .PHONY: test
 test:
-	PYTHONPATH=$(PYTHONPATH) poetry run pytest -c pyproject.toml --cov-report=html --cov=fake_vcf tests/
+	PYTHONPATH=$(PYTHONPATH) poetry run pytest -n auto -c pyproject.toml --cov-report=html --cov=fake_vcf tests/
 	poetry run coverage-badge -o assets/images/coverage.svg -f
 
 .PHONY: check-codestyle
diff --git a/poetry.lock b/poetry.lock
index 4e51ab7..00eea53 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -375,6 +375,20 @@ files = [
 [package.extras]
 test = ["pytest (>=6)"]
 
+[[package]]
+name = "execnet"
+version = "2.0.2"
+description = "execnet: rapid multi-Python deployment"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "execnet-2.0.2-py3-none-any.whl", hash = "sha256:88256416ae766bc9e8895c76a87928c0012183da3cc4fc18016e6f050e025f41"},
+    {file = "execnet-2.0.2.tar.gz", hash = "sha256:cc59bc4423742fd71ad227122eb0dd44db51efb3dc4095b45ac9a08c770096af"},
+]
+
+[package.extras]
+testing = ["hatch", "pre-commit", "pytest", "tox"]
+
 [[package]]
 name = "filelock"
 version = "3.13.1"
@@ -921,6 +935,26 @@ pytest = ">=7.0.0"
 [package.extras]
 test = ["black (>=22.1.0)", "flake8 (>=4.0.1)", "pre-commit (>=2.17.0)", "tox (>=3.24.5)"]
 
+[[package]]
+name = "pytest-xdist"
+version = "3.4.0"
+description = "pytest xdist plugin for distributed testing, most importantly across multiple CPUs"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "pytest-xdist-3.4.0.tar.gz", hash = "sha256:3a94a931dd9e268e0b871a877d09fe2efb6175c2c23d60d56a6001359002b832"},
+    {file = "pytest_xdist-3.4.0-py3-none-any.whl", hash = "sha256:e513118bf787677a427e025606f55e95937565e06dfaac8d87f55301e57ae607"},
+]
+
+[package.dependencies]
+execnet = ">=1.1"
+pytest = ">=6.2.0"
+
+[package.extras]
+psutil = ["psutil (>=3.0)"]
+setproctitle = ["setproctitle"]
+testing = ["filelock"]
+
 [[package]]
 name = "pyupgrade"
 version = "3.15.0"
@@ -1224,13 +1258,13 @@ files = [
 
 [[package]]
 name = "tomlkit"
-version = "0.12.2"
+version = "0.12.3"
 description = "Style preserving TOML library"
 optional = false
 python-versions = ">=3.7"
 files = [
-    {file = "tomlkit-0.12.2-py3-none-any.whl", hash = "sha256:eeea7ac7563faeab0a1ed8fe12c2e5a51c61f933f2502f7e9db0241a65163ad0"},
-    {file = "tomlkit-0.12.2.tar.gz", hash = "sha256:df32fab589a81f0d7dc525a4267b6d7a64ee99619cbd1eeb0fae32c1dd426977"},
+    {file = "tomlkit-0.12.3-py3-none-any.whl", hash = "sha256:b0a645a9156dc7cb5d3a1f0d4bab66db287fcb8e0430bdd4664a095ea16414ba"},
+    {file = "tomlkit-0.12.3.tar.gz", hash = "sha256:75baf5012d06501f07bee5bf8e801b9f343e7aac5a92581f20f80ce632e6b5a4"},
 ]
 
 [[package]]
@@ -1327,4 +1361,4 @@ test = ["covdefaults (>=2.3)", "coverage (>=7.2.7)", "coverage-enable-subprocess
 [metadata]
 lock-version = "2.0"
 python-versions = "^3.8.1"
-content-hash = "bf3818a93d158c0cee2f783f617d24c182f9ed18cd2ca5c60d8ee6365bf46f0e"
+content-hash = "7d373a74a0cb11b5cd469693c16edb034c5147bad460518f47d0e4a3cebd0c29"
diff --git a/pyproject.toml b/pyproject.toml
index f41f924..15ff327 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -72,6 +72,7 @@ pytest-html = "^4.1.1"
 pytest-cov = "^4.1.0"
 black = {version = "^23.11.0", allow-prereleases = true}
 safety = "^2.3.5"
+pytest-xdist = "^3.4.0"
 
 [tool.black]
 # https://github.com/psf/black
diff --git a/tests/test_example/test_vcf_validator.py b/tests/test_example/test_vcf_validator.py
index f1c49e0..7e09a0e 100644
--- a/tests/test_example/test_vcf_validator.py
+++ b/tests/test_example/test_vcf_validator.py
@@ -1,3 +1,4 @@
+import itertools
 import platform
 import stat
 import subprocess
@@ -52,17 +53,30 @@ def run_vcf_validator(vcf_file_path, result_path):
 
 
 @pytest.mark.parametrize(
-    ("cli_args",),
-    [
-        (["-r", "10", "--no-large-format"],),
-        (["-r", "50", "--no-large-format"],),
-        (["-r", "100", "--no-large-format"],),
-        (["-r", "10", "--large-format"],),
-    ],
+    "cli_args",
+    list(
+        itertools.product(
+            *[
+                [["-r", f"{r}"] for r in range(1, 100, 25)],
+                [["-s", f"{s}"] for s in range(1, 100, 25)],
+                ["--large-format", "--no-large-format"],
+                ["--phased", "--no-phased"],
+                [[f"-c", f"chr{c}"] for c in range(1, 23)],
+            ]
+        )
+    ),
 )
-def test_vcf_file_validation(cli_args: list, tmp_path):
+def test_vcf_file_validation(cli_args: tuple, tmp_path):
     vcf_file_path = tmp_path / "example.vcf"
-    args = cli_args + ["-o", vcf_file_path]
+    args = []
+    for cli_arg in cli_args:
+        if type(cli_arg) is list:
+            args += cli_arg
+        else:
+            args += [cli_arg]
+
+    args += ["-o", vcf_file_path]
+
     runner.invoke(app, args=args)
 
     validator_status, validation_result = run_vcf_validator(