diff --git a/.env b/.env
new file mode 100644
index 0000000..d3c66d6
--- /dev/null
+++ b/.env
@@ -0,0 +1 @@
+DEFAULT_PATH=tests
\ No newline at end of file
diff --git a/.github/CONTRIBUTIONS.md b/.github/CONTRIBUTIONS.md
new file mode 100644
index 0000000..306974f
--- /dev/null
+++ b/.github/CONTRIBUTIONS.md
@@ -0,0 +1,13 @@
+# Testing
+
+Tests written in [bashunit](https://bashunit.typeddevs.com/).
+
+Install vendor dependencies:
+```bash
+./install-dependencies.sh
+```
+
+Run all tests:
+```bash
+./lib/bashunit tests
+```
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..a24380b
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,19 @@
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+name: Tests
+jobs:
+  tests:
+    name: "Run tests"
+    runs-on: 'ubuntu-latest'
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: "Install dependencies"
+        run: ./install-dependencies.sh
+
+      - name: "Tests"
+        run: ./lib/bashunit
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a5c1afb
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+.idea/
+
+lib/bashunit
diff --git a/install-dependencies.sh b/install-dependencies.sh
new file mode 100755
index 0000000..b8d466d
--- /dev/null
+++ b/install-dependencies.sh
@@ -0,0 +1,4 @@
+#!/bin/bash
+
+## bashunit
+curl -s https://bashunit.typeddevs.com/install.sh | bash -s -- lib 0.10.0
diff --git a/tests/fixtures/test_should_ignore_files_with_regex_response b/tests/fixtures/test_should_ignore_files_with_regex_response
new file mode 100644
index 0000000..b6af2cd
--- /dev/null
+++ b/tests/fixtures/test_should_ignore_files_with_regex_response
@@ -0,0 +1,74 @@
+[
+  {
+    "filename": ".editorconfig",
+    "additions": 9,
+    "deletions": 0,
+    "changes": 9
+  },
+  {
+    "filename": ".github/workflows/ci.yml",
+    "additions": 17,
+    "deletions": 0,
+    "changes": 17
+  },
+  {
+    "filename": "asdasdasd.lock",
+    "additions": 1188,
+    "deletions": 0,
+    "changes": 1188
+  },
+  {
+    "filename": "entrypoint.sh",
+    "additions": 4,
+    "deletions": 4,
+    "changes": 8
+  },
+  {
+    "filename": "src/ensure.sh",
+    "additions": 4,
+    "deletions": 4,
+    "changes": 8
+  },
+  {
+    "filename": "src/github.sh",
+    "additions": 89,
+    "deletions": 76,
+    "changes": 165
+  },
+  {
+    "filename": "src/github_actions.sh",
+    "additions": 1,
+    "deletions": 1,
+    "changes": 2
+  },
+  {
+    "filename": "src/inner.lock",
+    "additions": 1188,
+    "deletions": 0,
+    "changes": 1188
+  },
+  {
+    "filename": "src/labeler.sh",
+    "additions": 48,
+    "deletions": 48,
+    "changes": 96
+  },
+  {
+    "filename": "src/log.sh",
+    "additions": 17,
+    "deletions": 0,
+    "changes": 17
+  },
+  {
+    "filename": "src/main.sh",
+    "additions": 34,
+    "deletions": 23,
+    "changes": 57
+  },
+  {
+    "filename": "src/misc.sh",
+    "additions": 10,
+    "deletions": 14,
+    "changes": 24
+  }
+]
\ No newline at end of file
diff --git a/tests/github_test.sh b/tests/github_test.sh
new file mode 100644
index 0000000..408b11b
--- /dev/null
+++ b/tests/github_test.sh
@@ -0,0 +1,14 @@
+#!/bin/bash
+
+function set_up() {
+  source ./src/misc.sh
+  source ./src/github.sh
+}
+
+function test_should_ignore_files_with_glob() {
+  local -r pr_number=123
+  local -r files_to_ignore=("*.lock" ".editorconfig")
+  mock curl cat ./tests/fixtures/test_should_ignore_files_with_regex_response
+
+  assert_match_snapshot "$(github::calculate_total_modifications "$pr_number" "${files_to_ignore[*]}")"
+}
diff --git a/tests/snapshots/github_test_sh.test_should_ignore_files_with_glob.snapshot b/tests/snapshots/github_test_sh.test_should_ignore_files_with_glob.snapshot
new file mode 100644
index 0000000..0ca45a0
--- /dev/null
+++ b/tests/snapshots/github_test_sh.test_should_ignore_files_with_glob.snapshot
@@ -0,0 +1 @@
+394