BDD and JBehave

I've been in my new job for a few weeks now and encountered Behavior Driven Development in the code I'm looking at, using JBehave.

BDD is a way of structuring unit tests in such a way as to make them more human-readable. Typically, a conventional unit test looks something like this (this is for a small builder class I’ve created):

@Test
public void testOneWhere() {
    //select with one criteria
    SQLBuilder instance = new SQLBuilder();
    instance.select().table("A_TABLE");
    String result = instance.where("A_COLUMN", "A_VALUE").build();
    assertTrue("result is not proper SQL: " + result,
            result.equals("SELECT * FROM A_TABLE 
                           WHERE A_COLUMN = \"A_VALUE\""));
}

This is quite a small test, but it’s easy to see that someone non-technical would have difficulty following what was going on here. Plus it’s not very flexible: if you want to test boundary conditions, for example, you either have to do a lot of cut-and-pasting or some fancy footwork with the test libraries.

Compare this to the equivalent BDD statement (called stories):

Scenario: with a where clause

Given a new SQLBuilder object
When select is called
And table is set to A_TABLE
And where is set to A_COLUMN equals A_VALUE
And build is called
Then the result is SELECT * FROM TABLE WHERE A_COLUMN = "A_VALUE"

This is supported in the test harness by methods bound to the statements in the story:

@When("select is called")
public void selectIsCalled() {
    sqlBuilder.select();
}

@When("table is set to $table")
public void tableSetToTable(String table){
    sqlBuilder.table(table);
} //etc.

Not only is the story more readable, but you can parameterise the calls, setting up tables of inputs and expected outputs. Nice.