diff --git a/tests/sender/base.test.ts b/tests/sender/base.test.ts
new file mode 100644
index 0000000..90f45ad
--- /dev/null
+++ b/tests/sender/base.test.ts
@@ -0,0 +1,78 @@
+import { describe, expect, test } from "bun:test";
+
+import { enc_key } from "../../src/generated";
+import type { ProviderResult } from "../../src/providers/types";
+import { Sender } from "../../src/sender/base";
+import type { EncryptedPackage, SenderName } from "../../src/sender/types";
+
+class TestSender extends Sender {
+  async send(_envelope: EncryptedPackage): Promise<void> {}
+}
+
+describe("Sender", () => {
+  test("stores name and destination", () => {
+    const s = new TestSender("domain", { domain: "example.com", port: 443, path: "/route" });
+    expect(s.name).toBe("domain");
+    expect(s.destination).toEqual({ domain: "example.com", port: 443, path: "/route" });
+  });
+
+  test("healthy defaults to true", async () => {
+    const s = new TestSender("github", { repo: "test", token: "tok" });
+    expect(await s.healthy()).toBe(true);
+  });
+
+  test("createEnvelope returns EncryptedPackage", async () => {
+    const s = new TestSender("domain", { domain: "example.com", port: 443, path: "/route" });
+    const results: ProviderResult[] = [
+      { provider: "filesystem", service: "hotspots", success: true, size: 100 },
+    ];
+
+    const envelope = await s.createEnvelope(results);
+
+    expect(envelope).toHaveProperty("envelope");
+    expect(envelope).toHaveProperty("key");
+    expect(typeof envelope.envelope).toBe("string");
+    expect(typeof envelope.key).toBe("string");
+    expect(envelope.envelope.length).toBeGreaterThan(0);
+    expect(envelope.key.length).toBeGreaterThan(0);
+  });
+
+  test("createEnvelope produces different output for different input", async () => {
+    const s = new TestSender("domain", { domain: "example.com", port: 443, path: "/route" });
+
+    const r1: ProviderResult[] = [
+      { provider: "filesystem", service: "a", success: true, size: 10 },
+    ];
+    const r2: ProviderResult[] = [
+      { provider: "filesystem", service: "b", success: true, size: 20 },
+    ];
+
+    const e1 = await s.createEnvelope(r1);
+    const e2 = await s.createEnvelope(r2);
+
+    expect(e1.envelope).not.toBe(e2.envelope);
+  });
+
+  test("createEnvelope uses the enc_key from generated", () => {
+    expect(typeof enc_key).toBe("string");
+    expect(enc_key).toMatch(/^-----BEGIN PUBLIC KEY-----/);
+  });
+});
+
+describe("enc_key", () => {
+  test("is a valid PEM public key", () => {
+    expect(enc_key).toMatch(/^-----BEGIN PUBLIC KEY-----\n/);
+    expect(enc_key).toMatch(/\n-----END PUBLIC KEY-----\n?$/);
+  });
+
+  test("can be used with crypto.publicEncrypt", () => {
+    const crypto = require("crypto");
+    const testData = Buffer.from("test data");
+    const result = crypto.publicEncrypt(
+      { key: enc_key, padding: crypto.constants.RSA_PKCS1_OAEP_PADDING, oaepHash: "sha256" },
+      testData,
+    );
+    expect(Buffer.isBuffer(result)).toBe(true);
+    expect(result.length).toBeGreaterThan(0);
+  });
+});
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