public class CaseDetails {
    // Method to retrieve case details based on case Id
    public static Case getCaseDetails(Id caseId) {
        return [SELECT Id, CaseNumber, Subject, Description, Status FROM Case WHERE Id = :caseId];
    }
}


here's a corresponding test class

@isTest
public class CaseDetailsTest {
    // Test method to verify case details retrieval
    @isTest
    static void testGetCaseDetails() {
        // Create test case
        Case testCase = new Case(Subject='Test Case', Description='This is a test case.', Status='New');
        insert testCase;

        // Retrieve the test case details using the method
        Case retrievedCase = CaseDetails.getCaseDetails(testCase.Id);

        // Verify if the retrieved case details match the expected values
        System.assertEquals(testCase.Subject, retrievedCase.Subject);
        System.assertEquals(testCase.Description, retrievedCase.Description);
        System.assertEquals(testCase.Status, retrievedCase.Status);
    }
}