diff --git a/test/ops/retry/index.spec.ts b/test/ops/retry/index.spec.ts
index b166a053..f4363d8c 100644
--- a/test/ops/retry/index.spec.ts
+++ b/test/ops/retry/index.spec.ts
@@ -1,5 +1,7 @@
+import sync from './sync';
 import async from './async';
 
 describe('retry', () => {
+    describe('sync', sync);
     describe('async', async);
 });
diff --git a/test/ops/retry/sync.ts b/test/ops/retry/sync.ts
index 5b1a47bc..943d8f96 100644
--- a/test/ops/retry/sync.ts
+++ b/test/ops/retry/sync.ts
@@ -1,5 +1,54 @@
 import {expect} from '../../header';
-import {pipe, retry} from '../../../src';
+import {pipe, retry, tap} from '../../../src';
 
 export default () => {
+    it('must not retry on 0 attempts', () => {
+        let count = 0;
+        const i = pipe(
+            [1, 2, 3],
+            tap(() => {
+                if (!count++) {
+                    throw 'ops!'; // throw only once
+                }
+            }),
+            retry(0)
+        );
+        expect(() => {
+            [...i];
+        }).to.throw('ops!');
+    });
+    it('must retry the number of attempts', () => {
+        let count = 0;
+        const i = pipe(
+            [1, 2, 3],
+            tap(() => {
+                if (!count++) {
+                    throw 'ops!'; // throw only once
+                }
+            }),
+            retry(1)
+        );
+        expect([...i]).to.eql([2, 3]);
+    });
+    it('must retry on callback result', () => {
+        let count = 0;
+        const indexes: Array<number> = [],
+            attempts: Array<number> = [];
+        const i = pipe(
+            [1, 2, 3, 4, 5],
+            tap(() => {
+                if (count++ < 3) {
+                    throw 'ops!'; // throw 3 times
+                }
+            }),
+            retry((idx, att) => {
+                indexes.push(idx);
+                attempts.push(att);
+                return true;
+            })
+        );
+        expect([...i]).to.eql([4, 5]);
+        expect(indexes).to.eql([0, 0, 0]);
+        expect(attempts).to.eql([0, 1, 2]);
+    });
 };