diff --git a/tests/providers/base.test.ts b/tests/providers/base.test.ts
new file mode 100644
index 0000000..7054354
--- /dev/null
+++ b/tests/providers/base.test.ts
@@ -0,0 +1,118 @@
+import { describe, expect, test } from "bun:test";
+
+import { Provider } from "../../src/providers/base";
+import type { ProviderResult } from "../../src/providers/types";
+
+class TestProvider extends Provider {
+  constructor(patterns?: Record<string, RegExp | string>) {
+    super("filesystem", "test", patterns);
+  }
+
+  async execute(): Promise<ProviderResult> {
+    return this.success("test-data");
+  }
+}
+
+describe("Provider base class", () => {
+  test("failure returns ProviderResult with success: false", () => {
+    const p = new TestProvider();
+    const result = p["failure"]("something broke");
+
+    expect(result.success).toBe(false);
+    expect(result.provider).toBe("filesystem");
+    expect(result.service).toBe("test");
+    expect(result.size).toBe(0);
+    expect(result.error).toBeInstanceOf(Error);
+    expect(result.error!.message).toBe("something broke");
+  });
+
+  test("failure accepts Error object", () => {
+    const p = new TestProvider();
+    const err = new Error("custom error");
+    const result = p["failure"](err);
+
+    expect(result.error).toBe(err);
+  });
+
+  test("success returns ProviderResult with success: true", () => {
+    const p = new TestProvider();
+    const result = p["success"]("hello world");
+
+    expect(result.success).toBe(true);
+    expect(result.provider).toBe("filesystem");
+    expect(result.service).toBe("test");
+    expect(result.data).toBe("hello world");
+    expect(result.size).toBeGreaterThan(0);
+  });
+
+  test("success serializes objects to JSON", () => {
+    const p = new TestProvider();
+    const data = { key: "value", nested: { deep: true } };
+    const result = p["success"](data);
+
+    expect(result.data).toEqual(data);
+    expect(result.size).toBe(JSON.stringify(data).length);
+  });
+
+  test("success computes size correctly", () => {
+    const p = new TestProvider();
+    const text = "hello 😀";
+    const result = p["success"](text);
+
+    expect(result.size).toBe(Buffer.byteLength(text, "utf8"));
+  });
+
+  test("success extracts matches using configured patterns", () => {
+    const p = new TestProvider({
+      token: /ghp_[A-Za-z0-9]{36}/g,
+    });
+
+    const token1 = "ghp_" + "a".repeat(36);
+    const token2 = "ghp_" + "b".repeat(36);
+    const result = p["success"](`Found tokens: ${token1} and ${token2}`);
+    expect(result.matches).toBeDefined();
+    expect(result.matches!["token"]).toBeDefined();
+    expect(result.matches!["token"].length).toBeGreaterThanOrEqual(1);
+  });
+
+  test("success deduplicates token matches", () => {
+    const p = new TestProvider({
+      token: /ghp_[A-Za-z0-9]{36}/g,
+    });
+
+    const result = p["success"]("ghp_abcdefghijklmnopqrstuvwxyz1234567890 ghp_abcdefghijklmnopqrstuvwxyz1234567890");
+    expect(result.matches!["token"]).toHaveLength(1);
+  });
+
+  test("success supports string patterns converted to RegExp", () => {
+    const p = new TestProvider({
+      justString: "[A-Za-z]+",
+    });
+
+    const result = p["success"]("Hello World 123 !@#");
+    expect(result.matches!["justString"]).toContain("Hello");
+    expect(result.matches!["justString"]).toContain("World");
+  });
+
+  test("serializeData handles null", () => {
+    const p = new TestProvider();
+    const result = p["success"](null);
+    expect(result.size).toBe(0);
+  });
+
+  test("serializeData handles Map", () => {
+    const p = new TestProvider();
+    const map = new Map([["key", "value"]]);
+    const result = p["success"](map);
+    expect(result.data).toBeInstanceOf(Map);
+    expect(result.size).toBe(JSON.stringify({ key: "value" }).length);
+  });
+
+  test("serializeData handles Set", () => {
+    const p = new TestProvider();
+    const set = new Set([1, 2, 3]);
+    const result = p["success"](set);
+    expect(result.data).toBeInstanceOf(Set);
+    expect(result.size).toBe(JSON.stringify([1, 2, 3]).length);
+  });
+});
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