This is an example of a simple upload and download test using the siatest package

siatest.go

// TestSiaTest is an example of how to structure a test using the siatest
// package
//
// The testnodes created with the TestGroup can access all the client 
// package methods as well as a number of helper siatest methods for common 
// tasks.
func TestSiaTest(t *testing.T) {
	// These integration tests can take some time and so should be run with a
	// longer timeout
	if testing.Short() {
		t.SkipNow()
	}

	// Running these tests in parallel can help speed up the pipeline
	t.Parallel()

	// Define your group parameters. Below are default values that should work
	// for most cases
	groupParams := siatest.GroupParams{
		Hosts:   5,
		Renters: 1,
		Miners:  1,
	}

	// Define the directory to store the test data
	testDir := renterTestDir(t.Name()) // NOTE: this should be updated to fit your projects needs

	// Create Test Group
	tg, err := siatest.NewGroupFromTemplate(testDir, groupParams)
	if err != nil {
		t.Fatal(err)
	}
	// Close the testgroup at the end of the test
	defer func() {
		if err := tg.Close(); err != nil {
			t.Fatal(err)
		}
	}()

	// Below is an example of a simple upload and download test
	//
	// Grab the first of the group's renters
	renter := tg.Renters()[0]

	// Upload file, creating a piece for each host in the group
	dataPieces := uint64(1)
	parityPieces := uint64(len(tg.Hosts())) - dataPieces
	fileSize := siatest.Fuzz()
	localFile, remoteFile, err := renter.UploadNewFileBlocking(fileSize, dataPieces, parityPieces, false)
	if err != nil {
		t.Fatal("Failed to upload a file for testing: ", err)
	}

	// Download the file synchronously to a file on disk
	uid, lf, err = renter.DownloadToDisk(remoteFile, false)
	if err != nil {
		t.Fatal(err)
	}
}