In a Karate `Examples:` table, what does appending `!` to a column header do, and what type does that column's value have without it?

## The default is string, and that surprises people An `Examples:` table is text. Karate reads each cell, and unless the column says otherwise it binds the cell **verbatim as a string**. So this table gives you `age == '5'`: ```gherkin Examples: | name | age | | Bob | 5 | ``` `match age == 5` fails there, and the failure message shows `5` against `5`, because a message cannot draw quotation marks around a type. The single exception is an empty cell: a blank in a plain column binds `null`, which is deliberate — it is how you drive "this field is absent" rows. ## What `!` does Append an exclamation mark to the header and the column's type changes to *evaluated*: ```gherkin Examples: | name | age! | alive! | tags! | | Bob | 5 | true | ['a', 'b'] | ``` - `age` is the **number** `5`. - `alive` is the **boolean** `true`. - `tags` is a real **array**; `{ a: 1 }` in such a column is a real object, and `tags[0]` or `obj.a` work as you would expect. - The mark is **stripped from the name**. The variable is `age`, not `age!`. - A blank cell in an evaluated column still binds `null`, so `##(...)` removal patterns keep working across mixed rows. Mechanically Karate wraps anything that looks like JSON in parentheses and evaluates the cell as a JavaScript expression. That evaluation happens **when the table is read, before the scenario starts**, in a JavaScript engine that has none of the feature's variables in scope — so a hinted cell cannot reference something a `Background` or `karate-config.js` defined. ## The three things `!` does *not* do | Belief | Reality | |---|---| | It makes the column required | It says nothing about presence; a blank cell is still `null` | | It changes what `<age>` splices | `<age>` always splices the **raw cell text**, hint or not | | It works on a dynamic table | A single-cell dynamic table has no header, so there is nothing to hint | The middle row is the one that costs debugging time. The hint governs the *variable* Karate binds and the contents of `__row`; the angle-bracket placeholder is a text substitution done before the step runs and never consults the column type. In practice `* def x = <age>` and `* def x = age` can disagree: the placeholder pastes `5` into the step, which JavaScript then parses as a number, while the unhinted variable is the string `'5'`. ## The silent fallback If the JavaScript evaluation of a hinted cell throws, Karate does **not** fail the row. It catches the exception, logs it at trace level, and falls back to the raw string. So a column header of `name!` over a cell holding `Bob` quietly yields the string `'Bob'` — `Bob` is an undefined identifier, evaluation fails, the raw text is returned. Two consequences worth carrying into a review: 1. **A misplaced `!` is invisible.** Adding it to a column of bare words changes nothing you can see, so nobody removes it, and the next person assumes it is doing something. 2. **A typo in a hinted JSON cell degrades instead of erupting.** `{ a: 1 ` with the closing brace missing does not fail the row; it binds the malformed text as a string and the failure surfaces several steps later, wherever the value is finally used. Turning on trace logging for the run is the way to see those, because nothing louder is emitted. ## When to reach for it - **Numbers and booleans you will `match` strictly.** `match response.age == age` only works when both sides are numbers. - **Inline JSON per row.** A column of `{ "first": "Bob", "last": "Dylan" }` under `name!` gives each row a real object, which is far more readable than three flat columns you reassemble in a step. - **Nulls that must be nulls.** Combined with a blank cell, an evaluated column expresses "this row has no value here" without a sentinel string like `NONE`. Leave it off for anything that genuinely is text — names, ids, dates you compare as strings. The hint costs a JavaScript evaluation per cell per row, and on a column that never needed it, that is work for no benefit and one more silent fallback waiting to happen.