Many UEFA referees have failed the tests in Turkey

According to a UEFA source, an amount of almost 20 % of the officials who are joining the UEFA course in Turkey has failed the fitness tests. The total number of the referees, who failed, is not confirmed so far; according to some sources, Martin Atkinson (ENG), Firat Aydinus (TUR), Olegário Benquerenca (POR, due to a long injury), Marcin Borski (POL), Manuel Gräfe (GER), Daniele Orsato (ITA) and Aleksandar Stavrev have failed the tests.
Reference: UEFA referees prepare in Turkey

The tests UEFA has applied are the so called "Yo-Yo Intermittent Recovery Tests":

The Yo-Yo Intermittent Tests are similar to the Yo-Yo Endurance Test (a variation of the beep test), except in the intermittent tests the participants have a short active break (5 and 10 seconds for the intermittent endurance and intermittent recovery test, respectively). There are two versions of each Yo-Yo Intermittent Test, a beginners Level 1 and advanced level 2 (see details of the speeds and levels for the Yo-Yo Intermittent Recovery Test and Yo-Yo Intermittent Endurance Test). The Yo-Yo tests can be performed using the Team BeepTest software.

• purpose: The test evaluates an individual's ability to repeatedly perform intervals over a prolonged period of time, particularly for athletes from sports such as tennis, team handball, basketball and soccer or similar sports.

• procedure: Use cones to mark out three lines as per the diagram above; 20 meters and 2.5 (endurance test) or 5 meters (recovery test) apart. The subject starts on or behind the middle line, and begins running 20 m when instructed by the cd. This subject turns and returns to the starting point when signaled by the recorded beep. There is a active recovery period (5 and 10 seconds respectively for the endurance and recovery versions of the test) interjected between every 20 meter (out and back) shuttle, during which the subject must walk or jog around the other cone and return to the starting point. A warning is given when the subject does not complete a successful out and back shuttle in the allocated time, the subject is removed the next time they do not complete a successful shuttle. (see video example)

• variations: for each of the recovery and endurance intermittent etsts there are two levels: level 1 designed for lesser trained individuals and level 2 aimed at well trained and elite athletes and starting at a faster speed. Both test variations have increasing speeds throughout the test. See the Yo-Yo Intermittent Test Table for more details.
• scoring: The athlete's score is the total distance covered before they were unable to keep up with the recording. The Yo-Yo intermittent test usually takes between 6-20 minutes for level 1 and between 2-10 minutes for level 2. For more details see the speeds and distances for the Yo-Yo Intermittent Recovery Test and Yo-Yo Intermittent Endurance Test.There has been formula published for estimating VO2 max (ml/min/kg) from the Yo-Yo IR1 and IR2 test results (Bangsbo et al. 2008):

Yo-Yo IR1 test:VO2max (mL/min/kg) = IR1 distance (m) × 0.0084 + 36.4
Yo-Yo IR2 test: VO2max (mL/min/kg) = IR2 distance (m) × 0.0136 + 45.3

• target population: The yo-yo intermittent test was developed specifically for soccer players, though it is suitable for similar sports teams which are intermittent in nature. The level 1 test is designed for recreational level players, while the level 2 test is for elite soccer players. The test is not suitable for populations in which a maximal exercise test would be contraindicated.
• reliability: Test reliability would depend on how strictly the test is run, and the previous practice allowed for the subjects.
• advantages: Large groups can perform this test all at once for minimal costs.
• disadvantages: Practice and motivation levels can influence the score attained, and the scoring of when a person is out of the test can be subjective. As the test is usually conducted outside, the environmental conditions can also affect the results. The test cd must be purchased.
• other considerations: This test is a maximal test, which requires a reasonable level of fitness. It is not recommended for recreational athletes or people with health problems, injuries or low fitness levels. You may not have power where you want to conduct this test. If so, you need to ensure that the batteries of the audio player are fully charged.
• comments: This test was developed by the Danish soccer physiologist Jens Bangsbo and his colleagues. 
• how UEFA evaluates the results for Elite Referees (Yo-Yo IR Level 1 test):

EVALUATION	Very poor	Poor	Good	Very Good	Excellent
Speed	15:7-16:6	16:7-17:6	17:7-18:6	18:7-19:6	19:7-20:6
Distance	>1040	>1360	>1680	>2000	>2320
Shuttles	>26	>34	>42	>50	>58

the text is an excerpt from topendsports.com