Taking an English test largely depends on your goal and circumstances for doing so. To a large extent, determining which test to take is not in your hands, especially in situations where you need the score for specific official purposes.
This is a different case altogether where you need the test score for proof of your level in English Language or certification for your CV; here, you have the right to choose and more flexibility.
However, for the first case, the English test you will take largely depends on some conditions, thus:
The above helps you to know which of the tests to take among IELTS, TOEFL, and TOEIC.
Irrespective of how proficient and fluent you are in English, if you are a native of a country that doesn't recognize English as its national Language but desire to study in an English-speaking country, then there is a need to take a test to prove your skills.
The International English Language Test System (IELTS) and the Test Of English as a Foreign Language (TOEFL) are the two most widely used tests and are offered in test locations all over the world. They are accepted by thousands of universities and organizations. The results from the tests are both valid for two years.
IELTS comprises four sections: writing, reading, speaking, and listening, and requires a total of 2 hours 45 minutes to be completed. The listening section often uses British or Australian accents, which means that candidates are expected to get used to these accents. The scores are released on a scale of 1-9, with 9 being the expert proficiency.
TOEFL also comprises of the writing, reading, speaking, and listening parts, but it is done in sessions. Fifty minutes for writing, 60-80 minutes for reading, 60-90 minutes for listening, and 20 minutes for speaking. The speaking session doesn't need the presence of an examiner, but uses microphone recording, unlike the IELTS where you sit face to face with an examiner. The scores are released on an overall total of 120; 30 for each part.
TOEIC (The Test of English for International Communications) is business-based. This means that it has no relevance in university applications but strictly for work and business. It is used to measure the everyday English skills of people working in an international environment. Many Asian companies use it to test their employees' ability to work with English speaking clients. The score is also valid for two years.
So for the purpose of studying abroad or migrating to an English speaking country, IELTS and TOEFL are the tests to take, while TOEIC is for business and work purposes.
Generally, students from Japan and the French choose TOEIC, while IELTS is more prevalent among students from South America and the Middle East. Lastly, the test to choose depends on the goals and circumstances of the student. The most important thing, however, is to prepare well and be confident on the day of the test.