add random.go test to draw/isogrids pkg

package isogrids

import (

	"net/http"

	"net/http/httptest"

	"testing"

)

func TestRandom(t *testing.T) {

	rec := httptest.NewRecorder()

	Random(rec, key, colorTheme, 10, 10, 10, float64(50))

	if rec.Code != http.StatusOK {

		t.Errorf("returned %v. Expected %v.", rec.Code, http.StatusOK)

	}

}

func TestRandomGradient(t *testing.T) {

	rec := httptest.NewRecorder()

	RandomGradient(rec, key, colorTheme, 10, 10, 10)

	if rec.Code != http.StatusOK {

		t.Errorf("returned %v. Expected %v.", rec.Code, http.StatusOK)

	}

}

func TestRandomMirror(t *testing.T) {

	rec := httptest.NewRecorder()

	RandomMirror(rec, key, colorTheme, 10, float64(50))

	if rec.Code != http.StatusOK {

		t.Errorf("returned %v. Expected %v.", rec.Code, http.StatusOK)

	}

}