UserInfo.getProfileId() Returns Invalid Profile ID in Apex Test Class (API v41.0 and Later)

This behavior is Working as Designed (WAD). With the introduction of API v41.0, two internal users were added to the system: "Automated Process" and "Data.com Clean." These are non-standard users without normal profiles, used for internal operations. At API v41.0 and later, these users are available in the test class context and may be loaded instead of the expected user from API v40.0 or lower, causing the profile query to fail.
The fix is to create a test user in the Apex test class and run the profile-dependent logic within System.runAs(testUser), instead of relying on UserInfo.getProfileId() in the context of internal system users.

Non-Working Scenario (API v41.0+)

The following pattern fails because the test runs in the context of the "Automated Process" internal user, which has no standard profile: 

@isTest(SeeAllData = false)
private class ProfileCheckTest {
    static testMethod void testStartDate() {
        User usr = [SELECT Id FROM User WHERE Name ='Automated Process' limit 1];
        System.runAs(usr) {
            String profileName = [SELECT Name FROM Profile WHERE Id =: UserInfo.getProfileId() LIMIT 1].Name;
        }
    }
}

In this scenario, UserInfo.getProfileId() returns the non-standard profile ID of the Automated Process user. The SOQL query for Profile returns no results, causing the test to fail.

Working Scenario — Create a Test User

The correct approach creates a test user with an explicitly assigned profile, then runs the logic within that user's context:

@isTest(SeeAllData = false)
private class ProfileCheckTest {
    static testMethod void testStartDate() {
        User usr = new User();
        usr.ProfileId = [SELECT Id FROM Profile WHERE Name != 'System Administrator' limit 1].Id;                   
        usr.LastName = 'Test';
        usr.Email = 'test@test.com';
        usr.Username = 'test@test.com' + System.currentTimeMillis();
        usr.CompanyName = 'Salesforce';
        usr.Title = 'Title';
        usr.Alias = 'Roger';
        usr.TimeZoneSidKey = 'America/Los_Angeles';
        usr.EmailEncodingKey = 'UTF-8';
        usr.LanguageLocaleKey = 'en_US';
        usr.LocaleSidKey = 'en_US';

        System.runAs(usr) {
            String profileName = [SELECT Name FROM Profile WHERE Id =: UserInfo.getProfileId() LIMIT 1].Name;
        }
    }
}

n this scenario, a new test user is created with an explicitly assigned Profile ID. When System.runAs(usr) runs, UserInfo.getProfileId() returns the assigned profile ID — not an internal user's ID — so the SOQL query succeeds.
Note: The code samples above are examples. Review and modify them for your specific organization's requirements.