diff --git a/.gitignore b/.gitignore
index 737953e..b73442f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,7 @@ __pycache__
 /dist
 *.egg-info
 gtk-blueprint-tool.pc
+
+/.coverage
+/htmlcov
+.mypy_cache
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b03f983..a78779f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -6,8 +6,10 @@ build:
   stage: build
   script:
     - dnf install -y meson python3-pip gtk4-devel gobject-introspection-devel
-    - pip3 install furo mypy sphinx
+    - pip3 install furo mypy sphinx coverage
     - mypy gtkblueprinttool
+    - coverage run -m unittest
+    - coverage html
     - meson _build -Ddocs=true
     - ninja -C _build
     - ninja -C _build test
@@ -15,6 +17,7 @@ build:
   artifacts:
     paths:
       - _build
+      - htmlcov
 
 pages:
   stage: pages
@@ -22,6 +25,7 @@ pages:
     - build
   script:
     - mv _build/docs/en public
+    - mv htmlcov public/coverage
   artifacts:
     paths:
       - public
diff --git a/tests/sample_errors/conflicting_namespaces.blp b/tests/sample_errors/conflicting_namespaces.blp
deleted file mode 100644
index 6ceefac..0000000
--- a/tests/sample_errors/conflicting_namespaces.blp
+++ /dev/null
@@ -1,2 +0,0 @@
-using Gtk 4.0;
-using Gtk 3.0;
diff --git a/tests/sample_errors/conflicting_namespaces.err b/tests/sample_errors/conflicting_namespaces.err
deleted file mode 100644
index c4c786e..0000000
--- a/tests/sample_errors/conflicting_namespaces.err
+++ /dev/null
@@ -1 +0,0 @@
-2,7,7,Namespace Gtk-3.0 can't be imported because version 4.0 was imported earlier
diff --git a/tests/sample_errors/using_gtk_3.blp b/tests/sample_errors/using_gtk_3.blp
deleted file mode 100644
index 440b006..0000000
--- a/tests/sample_errors/using_gtk_3.blp
+++ /dev/null
@@ -1 +0,0 @@
-using Gtk 3.0;
diff --git a/tests/sample_errors/using_gtk_3.err b/tests/sample_errors/using_gtk_3.err
deleted file mode 100644
index e6d99ee..0000000
--- a/tests/sample_errors/using_gtk_3.err
+++ /dev/null
@@ -1 +0,0 @@
-1,11,3,Only GTK 4 is supported
diff --git a/tests/test_samples.py b/tests/test_samples.py
index c338208..f2c7a13 100644
--- a/tests/test_samples.py
+++ b/tests/test_samples.py
@@ -103,8 +103,6 @@ class TestSamples(unittest.TestCase):
 
 
     def test_sample_errors(self):
-        self.assert_sample_error("conflicting_namespaces")
         self.assert_sample_error("duplicate_obj_id")
         self.assert_sample_error("two_templates")
-        self.assert_sample_error("using_gtk_3")
         self.assert_sample_error("using_invalid_namespace")