Table Diff

Compare expected vs actual tables with readable, Cucumber-style output.

diff() always raises TableDiffError when the tables differ. If you want to check whether they match without raising, catch the exception.

Basic diff

from behave_data import diff, TableDiffError

@then("the actual table matches expected")
def step_actual_matches(context):
    diff(context.expected_table, context.actual_table)

If tables differ, the raised TableDiffError contains output similar to:

Tables were not identical:
      - | Alice | 30 |
      + | Bob | 30 |

Check diff without failing

from behave_data import diff, TableDiffError

@then("the tables match")
def step_check_diff(context):
    try:
        diff(context.expected_table, context.actual_table)
    except TableDiffError as exc:
        print("Tables differ:", exc)
        raise

Ignore columns

diff(
    context.expected_table,
    context.actual_table,
    ignore_columns=["created_at", "id"],
)

Unordered comparison

diff(context.expected_table, context.actual_table, ordered=False)

Surplus columns

By default, extra columns in the actual table cause a diff. Disable with:

diff(context.expected_table, context.actual_table, surplus_columns=False)

Diff in features

Feature: Table comparison

  Scenario: Prices should match
    Given an expected price list
      | name:str | price:float |
      | Apple    | 1.50        |
    When the actual price list is
      | name:str | price:float |
      | Apple    | 1.50        |
    Then the prices should match

from behave_data import diff

@given("an expected price list")
def step_expected(context):
    context.expected = context.table

@when("the actual price list is")
def step_actual(context):
    context.actual = context.table

@then("the prices should match")
def step_match(context):
    diff(context.expected, context.actual)

Diff with list of dicts

actual can be a list[dict], a single dict, or a table-like object. list[list] is not supported because headers are required.

from behave_data import diff

expected = context.table
actual = [
    {"name": "Apple", "price": "1.50"},
]
diff(expected, actual)

Diff an empty table

from behave_data import diff

# actual is an empty list of dicts with expected headers
diff(context.expected_table, [])