Achieve 100% test coverage

internal_test.go

@@ -0,0 +1,12 @@
+package puddle
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRemoveResourcePanicsWithBugReportIfResourceDoesNotExist(t *testing.T) {
+	s := []*Resource{new(Resource), new(Resource), new(Resource)}
+	assert.PanicsWithValue(t, "BUG: removeResource could not find res in slice", func() { removeResource(s, new(Resource)) })
+}

pool.go

@@ -368,7 +368,7 @@ func removeResource(slice []*Resource, res *Resource) []*Resource {
 		}
 	}
 
-	return slice
+	panic("BUG: removeResource could not find res in slice")
 }
 
 func (p *Pool) constructResourceValue(ctx context.Context) (interface{}, error) {

pool_test.go

@@ -455,6 +455,10 @@ func TestResourceDestroyRemovesResourceFromPool(t *testing.T) {
 
 	assert.Equal(t, 0, pool.Stat().TotalResources())
 	assert.Equal(t, 0, destructorCalls.Value())
+
+	// Can still call Value and CreationTime
+	res.Value()
+	res.CreationTime()
 }
 
 func TestResourceHijackRemovesResourceFromPoolButDoesNotDestroy(t *testing.T) {
@@ -470,6 +474,21 @@ func TestResourceHijackRemovesResourceFromPoolButDoesNotDestroy(t *testing.T) {
 	assert.Equal(t, 0, pool.Stat().TotalResources())
 }
 
+func TestResourcePanicsOnUsageWhenNotAcquired(t *testing.T) {
+	constructor, _ := createConstructor()
+	pool := puddle.NewPool(constructor, stubDestructor, 10)
+
+	res, err := pool.Acquire(context.Background())
+	require.NoError(t, err)
+	res.Release()
+
+	assert.PanicsWithValue(t, "tried to release resource that is not acquired", res.Release)
+	assert.PanicsWithValue(t, "tried to destroy resource that is not acquired", res.Destroy)
+	assert.PanicsWithValue(t, "tried to hijack resource that is not acquired", res.Hijack)
+	assert.PanicsWithValue(t, "tried to access resource that is not acquired or hijacked", func() { res.Value() })
+	assert.PanicsWithValue(t, "tried to access resource that is not acquired or hijacked", func() { res.CreationTime() })
+}
+
 func TestPoolAcquireReturnsErrorWhenPoolIsClosed(t *testing.T) {
 	constructor, _ := createConstructor()
 	pool := puddle.NewPool(constructor, stubDestructor, 10)