should I buy milk
cash in wallet credit card pints of milk remaining go to store?
0 no 0 no
10 no 0 yes
0 yes 0 yes
10 yes 0 yes
0 no 1 no
10 no 1 no
0 yes 1 no
10 yes 1 nope

This is a decision table; sometimes known as a truth table. This particular table has three inputs and one output.

Here is the fixture code that it invokes:
package fitnesse.slim.test;

public class ShouldIBuyMilk {
  private int dollars;
  private int pints;
  private boolean creditCard;

  public void setCashInWallet(int dollars) {
    this.dollars = dollars;

  public void setPintsOfMilkRemaining(int pints) {
    this.pints = pints;

  public void setCreditCard(String valid) {
    creditCard = "yes".equals(valid);

  public String goToStore() {
    return (pints == 0 && (dollars > 2 || creditCard)) ? "yes" : "no";

  // The following functions are optional.  If they aren't declared they'll be ignored.
  public void execute() {

  public void reset() {

  public void table(List<List<String>> table) {

  public void beginTable() {

  public void endTable() {

That pretty much explains it all. But let's look at the details a bit more closely.

First of all, there's the name of the table: "should I buy milk". This is named for a decision to be made. That's good style. Decision tables should be named for decisions. However that name also translates to the fixture class ShouldIBuyMilk. If you run this test you'll notice that the name turns green. This means that Slim found the fixture class and was able to create an instance of it.

The first cell could also have been Decision:should I buy milk, DT:should I buy milk, or ShouldIBuyMilk, etc.. The code Decision: or DT: tells Slim what kind of table this is. Decision table is the default.

Next, there's the row of column headers. If you look carefully at them you'll see that they all correspond to functions in the fixture class. However, the first three correspond to set functions. That's because they don't have a ?. The Decision Table considers them to be inputs, and automatically calls the appropriately named set function.

The last column header does have a ?. Decision Table considers it to be an output and so calls it as a function and expects a return value. That return value is compared to the contents of the column and turns the corresponding cell red or green depending whether it matches. Note that the cell that contains 'nope' does not match the 'no' that is returned.

The flow is very simple.

  1. First the ShouldIBuyMilk fixture is constructed.
  2. Next the table method is called if it exists. (see below).
  3. Next the beginTable method is called, if it exists. Use this for initializations if you want to.
  4. Then for each row in the table:
    1. First the reset function is called (if present), just in case you want to prepare or clean up.
    2. Then all the inputs are loaded by calling the appropriate set functions. Inputs are loaded in the left to right order of their appearance in the header.
    3. Then the execute function of the fixture is called (if present).
    4. Finally all the output functions are called, again in left to right order, and the return values compared to their table cells.
  5. Finally the endTable method is called, if it exists. Use this for closedown and cleanup if you want to.

Optional Functions

There's not much more to it than that.

Well, yes there is.

But for that you should look at Symbols In Tables and Value Comparisons


When exceptions occur in a decision table, they're displayed in line.

should I buy milk
cash in wallet credit card pints of milk remaining go to store?
0 yes 1 no
0 yes one no

decision table all done wrong
foo bar baz?
- /


If you want to document the data given in a particular row you can just add an extra cell to the right.

should I buy milk
cash in wallet credit card pints of milk remaining go to store?
0 no 0 no
10 no 0 yes plenty of money but no need for a pint

For more detailed documentation you can add designated comment columns anywhere. Just prefix the header with a hash symbol.

should I buy milk
cash in wallet # comment credit card pints of milk remaining go to store?
-2 we actually allow negative amounts, meaning debt no 0 no
1 must have at least 2 euros no 0 no