This study attempts to predict the testability of Eclipse (one of the biggest open source project). Testability is an important attribute of software quality. Assessment of software testability can help in predicting the testing effort required for a given product. In this study the testability is predicted at package level. Eclipse is a project whose functional testing is done at the package level. We have developed an Eclipse plugin to extract the value of source code metrics and test metrics from the source code of Eclipse project. The source code metrics and test metrics of Eclipse project are calculated at the package level. Test metrics are obtained from the J unit test classes of test packages. The package level metrics are obtained from the class level metrics. A correlation is found between source code metrics and test metrics. The results show that there is a significant correlation between source code metrics and test metrics at the package level. Since, the test metrics assess the testing effort and through testing effort an assessment of testability is made. The results show that testability can be assessed from the source code metrics. This study can help software practitioners to have an understanding of package level testability and to assess the testing effort for a given package.