diff --git a/README.md b/README.md
index f3dac9e..402c637 100644
--- a/README.md
+++ b/README.md
@@ -921,8 +921,8 @@ This module provides some utility functions for more convenient work with Ever o
 ````typescript
 import { toNano, fromNano, getRandomNonce, convertAmount, isValidEverAddress, stringToBytesArray } from "locklift";
 
-toNano(10); // 10000000000
-fromNano(10000000000); // 10```
+toNano(10); // 10000000000 nano evers
+fromNano(10000000000); // 10 evers```
 ````
 
 ## Plugins
diff --git a/sample-project-typescript/contracts/Sample.tsol b/sample-project-typescript/contracts/Sample.tsol
index 3788dea..e0e548d 100644
--- a/sample-project-typescript/contracts/Sample.tsol
+++ b/sample-project-typescript/contracts/Sample.tsol
@@ -23,6 +23,10 @@ contract Sample {
         emit StateChange(_state);
     }
 
+    function fail() public {
+        require( 1 < 0, 101); // 100 is default error code, it is good to set non-default codes beforehand
+    }
+
     function getDetails()
         external
         view
diff --git a/sample-project-typescript/test/sample-test.ts b/sample-project-typescript/test/sample-test.ts
index 3384ee4..f1c2a6a 100644
--- a/sample-project-typescript/test/sample-test.ts
+++ b/sample-project-typescript/test/sample-test.ts
@@ -1,6 +1,9 @@
 import { expect } from "chai";
 import { Contract, Signer } from "locklift";
 import { FactorySource } from "../build/factorySource";
+import { lockliftChai } from "locklift";
+import chai from "chai";
+chai.use(lockliftChai);
 
 let sample: Contract<FactorySource["Sample"]>;
 let signer: Signer;
@@ -29,7 +32,7 @@ describe("Test Sample contract", async function () {
         constructorParams: {
           _state: INIT_STATE,
         },
-        value: locklift.utils.toNano(2),
+        value: locklift.utils.toNano(2), // converts 2 evers to nanos
       });
       sample = contract;
 
@@ -45,5 +48,13 @@ describe("Test Sample contract", async function () {
 
       expect(Number(response._state)).to.be.equal(NEW_STATE, "Wrong state");
     });
+
+    it("Test error tracing", async function () {
+      const { traceTree } = await locklift.tracing.trace(
+        await sample.methods.fail({}).sendExternal({ publicKey: signer.publicKey }),
+        {rise: false}
+      );
+      expect(traceTree).to.have.error(101);
+    });
   });
 });