capture.md

Capture a value

It's possible to capture some values when a value is compared with a capture object, a callback will be called.

This can be used in functional testing to easily capture a value from a JSON and then use this value later.

For example to compare and extract the id field of the following JSON

{
  "id": 4
}

You should use the following capture object

{
  "id": {
    "__capture": {
      "name": "someCaptureName",
      "type": "integer"
    }
  }
}

Example

Code

var jsonComparer = TestUtils.JsonComparer.JsonComparer.GetDefault(((captureName, token) => {
  Console.WriteLine($"Captured value: name={captureName} token={token}");
}));


const string expectedJson = @"{""a"":{""__capture"":{""name"": ""some-name"", ""type"":""integer""}}, ""b"":""abc""}";
const string actualJson = @"{""a"":42, ""b"":""abc""}";

var errors = jsonComparer.Compare(expectedJson, actualJson);
Console.WriteLine(JsonComparerOutputFormatter.GetReadableMessage(expectedJson, actualJson, errors));

Output

Captured value: name=some-name token=42
No differences found

Note

If there is any errors, to improve the readability of the output, the capture objects are replaced by their matching value in the expectedJToken.

Example

Code

var jsonComparer = TestUtils.JsonComparer.JsonComparer.GetDefault(((captureName, token) => {
  Console.WriteLine($"Captured value: name={captureName} token={token}");
}));

const string expectedJson = @"{""a"":{""__capture"":{""name"": ""some-name"", ""type"":""integer""}}, ""b"":""abc""}";
const string actualJson = @"{""a"":42, ""b"":""def""}";


var errors = jsonComparer.Compare(expectedJson, actualJson);
Console.WriteLine(JsonComparerOutputFormatter.GetReadableMessage(expectedJson, actualJson, errors));

Output

Captured value: name=some-name token=42
Given json does not match expected one:
  - b: Invalid value, expected 'abc' but found 'def'

--- expected
+++ actual
 {
   "a": 42,
-  "b": "abc"
+  "b": "def"
 }

Capture using regex

To match and capture value of field id

{
  "id": "B6E73AF8-BDB9-41B2-BB77-28575B08A28C"
}

{
  "id": {
    "__capture": {
      "name": "some-global-capture-name",
      "regex": "^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$"
    }
  }
}

Example

Code

var jsonComparer = TestUtils.JsonComparer.JsonComparer.GetDefault(((captureName, token) => {
    Console.WriteLine($"Captured value: name={captureName} token={token}");
}));

var expectedJson = JToken.Parse(@"{""a"":{""__capture"":{""name"": ""some-global-capture-name"", ""regex"":""^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$""}}}");
var actualJson = JToken.Parse(@"{""a"":""B6E73AF8-BDB9-41B2-BB77-28575B08A28C""}");

var errors = jsonComparer.Compare(expectedJson, actualJson);
Console.WriteLine(JsonComparerOutputFormatter.GetReadableMessage(expectedJson, actualJson, errors));

Output

Captured value: name=some-global-capture-name token=B6E73AF8-BDB9-41B2-BB77-28575B08A28C
No differences found

Capture using regex capture groups

Example 1

Code

var jsonComparer = TestUtils.JsonComparer.JsonComparer.GetDefault(((captureName, token) => {
    Console.WriteLine($"Captured value: name={captureName} token={token}");
}));

var expectedJson = JToken.Parse(@"{""a"":{""__capture"":{""name"": ""some-global-capture-name"", ""regex"":""(?<localCapture>bcd)""}}, ""b"":""def""}");
var actualJson = JToken.Parse(@"{""a"":""abcdef"", ""b"":""def""}");

var errors = jsonComparer.Compare(expectedJson, actualJson);
Console.WriteLine(JsonComparerOutputFormatter.GetReadableMessage(expectedJson, actualJson, errors));

Output

Captured value: name=some-global-capture-name token=abcdef
Captured value: name=localCapture token=bcd
No differences found

Example 2

Code

var jsonComparer = TestUtils.JsonComparer.JsonComparer.GetDefault(((captureName, token) => {
    Console.WriteLine($"Captured value: name={captureName} token={token}");
}));

var expectedJson = JToken.Parse(@"{""a"":{""__capture"":{""regex"":""(?<localCapture>bcd)""}}, ""b"":""def""}");
var actualJson = JToken.Parse(@"{""a"":""abcdef"", ""b"":""def""}");

var errors = jsonComparer.Compare(expectedJson, actualJson);
Console.WriteLine(JsonComparerOutputFormatter.GetReadableMessage(expectedJson, actualJson, errors));

Output

Captured value: name=localCapture token=bcd
No differences found