<h2 id="heading-assert-statement">Assert Statement :</h2>
<ul>
<li>During development, use an assert statement— <code>assert(&lt;condition&gt;, &lt;optionalMessage&gt;);</code> —to disrupt normal execution if a boolean condition is false.
</li>
<li><pre><code class="lang-dart"> // Make sure the variable has a non-null value.
 assert(text != null);

 // Make sure the value is less than 100.
 assert(number &lt; 100);

 // Make sure this is an https URL.
 assert(urlString.startsWith('https'));
</code></pre>
</li>
<li>To attach a message to an assertion, add a string as the second argument to <code>assert</code> (optionally with a trailing comma):
</li>
<li><pre><code class="lang-dart"> assert(urlString.startsWith('https'),
 'URL ($urlString) should start with "https".');
</code></pre>
</li>
<li>The first argument to <code>assert</code> can be any expression that resolves to a boolean value. If the expression's value is true, the assertion succeeds and execution continues. If it's false, the assertion fails and an exception (an <code>AssertionError</code>) is thrown.
</li>
</ul>

## Assert Statement :

* During development, use an assert statement— `assert(<condition>, <optionalMessage>);` —to disrupt normal execution if a boolean condition is false.
 
* ```dart
 // Make sure the variable has a non-null value.
 assert(text != null);
 
 // Make sure the value is less than 100.
 assert(number < 100);
 
 // Make sure this is an https URL.
 assert(urlString.startsWith('https'));
 ```
 
* To attach a message to an assertion, add a string as the second argument to `assert` (optionally with a trailing comma):
 
* ```dart
 assert(urlString.startsWith('https'),
 'URL ($urlString) should start with "https".');
 ```
 
* The first argument to `assert` can be any expression that resolves to a boolean value. If the expression's value is true, the assertion succeeds and execution continues. If it's false, the assertion fails and an exception (an `AssertionError`) is thrown.

Dart : Assert statement | Assertions

Assert Statement :