diff --git a/types/part_set_test.go b/types/part_set_test.go
index 01437f05e..3576e747e 100644
--- a/types/part_set_test.go
+++ b/types/part_set_test.go
@@ -1,10 +1,12 @@
 package types
 
 import (
-	"bytes"
 	"io/ioutil"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
 	cmn "github.com/tendermint/tendermint/libs/common"
 )
 
@@ -13,24 +15,21 @@ const (
 )
 
 func TestBasicPartSet(t *testing.T) {
-
 	// Construct random data of size partSize * 100
 	data := cmn.RandBytes(testPartSize * 100)
-
 	partSet := NewPartSetFromData(data, testPartSize)
-	if len(partSet.Hash()) == 0 {
-		t.Error("Expected to get hash")
-	}
-	if partSet.Total() != 100 {
-		t.Errorf("Expected to get 100 parts, but got %v", partSet.Total())
-	}
-	if !partSet.IsComplete() {
-		t.Errorf("PartSet should be complete")
-	}
+
+	assert.NotEmpty(t, partSet.Hash())
+	assert.Equal(t, 100, partSet.Total())
+	assert.Equal(t, 100, partSet.BitArray().Size())
+	assert.True(t, partSet.HashesTo(partSet.Hash()))
+	assert.True(t, partSet.IsComplete())
+	assert.Equal(t, 100, partSet.Count())
 
 	// Test adding parts to a new partSet.
 	partSet2 := NewPartSetFromHeader(partSet.Header())
 
+	assert.True(t, partSet2.HasHeader(partSet.Header()))
 	for i := 0; i < partSet.Total(); i++ {
 		part := partSet.GetPart(i)
 		//t.Logf("\n%v", part)
@@ -39,31 +38,28 @@ func TestBasicPartSet(t *testing.T) {
 			t.Errorf("Failed to add part %v, error: %v", i, err)
 		}
 	}
-
-	if !bytes.Equal(partSet.Hash(), partSet2.Hash()) {
-		t.Error("Expected to get same hash")
-	}
-	if partSet2.Total() != 100 {
-		t.Errorf("Expected to get 100 parts, but got %v", partSet2.Total())
-	}
-	if !partSet2.IsComplete() {
-		t.Errorf("Reconstructed PartSet should be complete")
-	}
+	// adding part with invalid index
+	added, err := partSet2.AddPart(&Part{Index: 10000})
+	assert.False(t, added)
+	assert.Error(t, err)
+	// adding existing part
+	added, err = partSet2.AddPart(partSet2.GetPart(0))
+	assert.False(t, added)
+	assert.Nil(t, err)
+
+	assert.Equal(t, partSet.Hash(), partSet2.Hash())
+	assert.Equal(t, 100, partSet2.Total())
+	assert.True(t, partSet2.IsComplete())
 
 	// Reconstruct data, assert that they are equal.
 	data2Reader := partSet2.GetReader()
 	data2, err := ioutil.ReadAll(data2Reader)
-	if err != nil {
-		t.Errorf("Error reading data2Reader: %v", err)
-	}
-	if !bytes.Equal(data, data2) {
-		t.Errorf("Got wrong data.")
-	}
+	require.NoError(t, err)
 
+	assert.Equal(t, data, data2)
 }
 
 func TestWrongProof(t *testing.T) {
-
 	// Construct random data of size partSize * 100
 	data := cmn.RandBytes(testPartSize * 100)
 	partSet := NewPartSetFromData(data, testPartSize)
@@ -86,5 +82,4 @@ func TestWrongProof(t *testing.T) {
 	if added || err == nil {
 		t.Errorf("Expected to fail adding a part with bad bytes.")
 	}
-
 }