What is TestVisible Annotation in Salesforce?

@TestVisible Annotation.

This annotation enables a more permissive access level for running tests only. TestVisible annotation allow test methods to access private or protected members of another class outside the test class. These members include methods, member variables, and inner classes.

• This example shows how to annotate a private class member variable and private method with TestVisible.

public class TestVisibleExample {
@TestVisible private static Integer recordNumber = 1;
@TestVisible private static void updateRecord(String name) {
}
}

• This is the test class that uses the previous class. It contains the test method that accesses the annotated member variable and method.

@isTest
private class TestVisibleExampleTest {
@isTest static void test1() {
// Access private variable annotated with TestVisible
Integer i = TestVisibleExample.recordNumber;
System.assertEquals(1, i);

// Access private method annotated with TestVisible
TestVisibleExample.updateRecord('RecordName');
// Perform some verification
}
}