diff --git a/plugins/cron/utils.test.ts b/plugins/cron/utils.test.ts
new file mode 100644
index 0000000..482eca7
--- /dev/null
+++ b/plugins/cron/utils.test.ts
@@ -0,0 +1,39 @@
+import { describe, it, expect } from 'vitest'
+import { parseCronExpression, getNextExecutionTime } from './utils'
+
+describe('cron utils', () => {
+    it('parseCronExpression parses a valid cron expression into an interval', () => {
+        const interval = parseCronExpression('0 0 * * *')
+        expect(interval).toBeDefined()
+        expect(typeof interval.next).toBe('function')
+    })
+
+    it('parseCronExpression throws on an invalid cron expression', () => {
+        expect(() => parseCronExpression('not a cron')).toThrow()
+    })
+
+    it('getNextExecutionTime returns the next minute boundary after the given time', () => {
+        const after = Date.UTC(2026, 0, 1, 12, 30, 30) // 2026-01-01 12:30:30 UTC
+        const next = getNextExecutionTime('* * * * *', after)
+
+        expect(next).toBeGreaterThan(after)
+        expect(next - after).toBeLessThanOrEqual(60_000)
+        // a "next minute" always lands on a whole-minute boundary
+        expect(next % 60_000).toBe(0)
+    })
+
+    it('getNextExecutionTime returns a future time for a daily cron', () => {
+        const after = Date.UTC(2026, 0, 1, 12, 0, 0)
+        const next = getNextExecutionTime('0 0 * * *', after)
+
+        expect(next).toBeGreaterThan(after)
+    })
+
+    it('getNextExecutionTime advances from one occurrence to the next', () => {
+        const after = Date.UTC(2026, 0, 1, 12, 0, 0)
+        const first = getNextExecutionTime('* * * * *', after)
+        const second = getNextExecutionTime('* * * * *', first)
+
+        expect(second).toBeGreaterThan(first)
+    })
+})
diff --git a/plugins/resend/index.test.ts b/plugins/resend/index.test.ts
new file mode 100644
index 0000000..a57d085
--- /dev/null
+++ b/plugins/resend/index.test.ts
@@ -0,0 +1,74 @@
+import { describe, it, expect, vi, afterEach } from 'vitest'
+import { ResendPlugin } from './index'
+
+describe('ResendPlugin', () => {
+    afterEach(() => {
+        vi.restoreAllMocks()
+    })
+
+    it('stores the provided api key', () => {
+        const plugin = new ResendPlugin({ apiKey: 'test-key' })
+        expect(plugin.apiKey).toBe('test-key')
+    })
+
+    it('is constructible without options (no api key)', () => {
+        const plugin = new ResendPlugin()
+        expect(plugin.apiKey).toBeUndefined()
+    })
+
+    it('sendEmail posts to the Resend API and returns the response data on success', async () => {
+        const fetchMock = vi.fn().mockResolvedValue({
+            ok: true,
+            json: async () => ({ id: 'email_123' }),
+        })
+        vi.stubGlobal('fetch', fetchMock)
+
+        const plugin = new ResendPlugin({ apiKey: 'test-key' })
+        const result = await plugin.sendEmail(
+            'from@example.com',
+            ['to@example.com'],
+            'Subject',
+            '<p>Hello</p>'
+        )
+
+        expect(result).toEqual({ id: 'email_123' })
+        expect(fetchMock).toHaveBeenCalledOnce()
+
+        const [url, options] = fetchMock.mock.calls[0]
+        expect(url).toBe('https://api.resend.com/emails')
+        expect(options.method).toBe('POST')
+        expect(options.headers.Authorization).toBe('Bearer test-key')
+        expect(JSON.parse(options.body)).toEqual({
+            from: 'from@example.com',
+            to: ['to@example.com'],
+            subject: 'Subject',
+            html: '<p>Hello</p>',
+        })
+    })
+
+    it('sendEmail throws with the API error message when the response is not ok', async () => {
+        const fetchMock = vi.fn().mockResolvedValue({
+            ok: false,
+            json: async () => ({ message: 'Invalid API key' }),
+        })
+        vi.stubGlobal('fetch', fetchMock)
+
+        const plugin = new ResendPlugin({ apiKey: 'bad-key' })
+        await expect(
+            plugin.sendEmail('a@b.com', ['c@d.com'], 'S', '<p>x</p>')
+        ).rejects.toThrow('Invalid API key')
+    })
+
+    it('sendEmail throws a default message when the error response has no message', async () => {
+        const fetchMock = vi.fn().mockResolvedValue({
+            ok: false,
+            json: async () => ({}),
+        })
+        vi.stubGlobal('fetch', fetchMock)
+
+        const plugin = new ResendPlugin({ apiKey: 'bad-key' })
+        await expect(
+            plugin.sendEmail('a@b.com', ['c@d.com'], 'S', '<p>x</p>')
+        ).rejects.toThrow('Failed to send email')
+    })
+})