The invention includes a method for testing a spreadsheet cell. Du-associations are collected for the spreadsheet cell. The cell's execution trace is tracked. After the user validates the cell, the du-associations that participated in the execution trace are marked as executed. Du-associations for other cells that are affected by the testing a spreadsheet cell are similarly marking as exercised. If the user changes a cell's contents, the collected du-associations for the cell are discarded and the steps of collecting test elements, tracking execution traces, and marking are repeated. Cells that depend on the changed cell also repeat these steps. After the user marks a cell as validated, a validation symbol is shown on the cell. If the cell's validation status is later brought into question, the validation symbol can change or be removed entirely. The invention also includes a method for providing a user with feedback of the testedness of the spreadsheet cells. The du-associations for each spreadsheet cell are maintained, and the subset of du-associations that have been exercised is identified. Using the numbers of tested and untested du-associations, a testedness measure is calculated for the cell, which is provided to the user.