diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index dc6ff53..4534f1c 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -50,7 +50,7 @@ jobs:
         run: deno run check
 
       - name: Test
-        run: deno test
+        run: deno run test
 
       - name: Publish dry run
         run: deno publish --dry-run
diff --git a/check-required-env/check-required-env.test.ts b/check-required-env/check-required-env.test.ts
new file mode 100644
index 0000000..f408b94
--- /dev/null
+++ b/check-required-env/check-required-env.test.ts
@@ -0,0 +1,45 @@
+import process from 'node:process'
+import { test } from '@cross/test'
+import { assertEquals, assertExists } from '@std/assert'
+
+import { checkRequiredEnv } from './check-required-env.ts'
+
+test('checkRequiredEnv - returns when env variable exists', () => {
+	// Setup
+	const testVarName = 'TEST_ENV_VAR'
+	process.env[testVarName] = 'test-value'
+
+	// Test
+	checkRequiredEnv(testVarName)
+
+	// Verify
+	assertExists(process.env[testVarName])
+
+	// Cleanup
+	delete process.env[testVarName]
+})
+
+test('checkRequiredEnv - exits when env variable is missing', () => {
+	// Setup
+	const testVarName = 'MISSING_ENV_VAR'
+	const originalExit = process.exit
+	let exitCalled = false
+	let exitCode: number | undefined
+
+	// Mock process.exit
+	process.exit = ((code?: number) => {
+		exitCalled = true
+		exitCode = code
+		// Don't actually exit
+	}) as typeof process.exit
+
+	// Test
+	checkRequiredEnv(testVarName)
+
+	// Verify
+	assertEquals(exitCalled, true)
+	assertEquals(exitCode, 1)
+
+	// Cleanup
+	process.exit = originalExit
+})
diff --git a/dates/dates.test.ts b/dates/dates.test.ts
index ddf7a69..2c581db 100644
--- a/dates/dates.test.ts
+++ b/dates/dates.test.ts
@@ -1,5 +1,6 @@
 import { test } from '@cross/test'
 import { assert, assertEquals } from '@std/assert'
+
 import {
 	DateTime,
 	getDateHourMinutes,
diff --git a/deno.jsonc b/deno.jsonc
index 20a6d35..74a9f66 100644
--- a/deno.jsonc
+++ b/deno.jsonc
@@ -15,7 +15,8 @@
 		"exclude": ["**/*.md", "**/*.yml", "**/*.yaml"]
 	},
 	"tasks": {
-		"check": "deno fmt --check && deno lint && biome lint"
+		"check": "deno fmt --check && deno lint && biome lint",
+		"test": "deno test --allow-sys --allow-env"
 	},
 	"lint": {
 		"rules": {