Anonymous apex to create test suite

createTestSuite.cls

class Membership {
  Id apexClassId;
  Id apexTestSuiteId;
  public Membership(Id suiteId, Id classId) {
    this.apexTestSuiteId = suiteId;
    this.apexClassId = classId;
  }
}

String suiteName = 'My_Test_Suite';
List<String> classNames = 'MyClassOneTest,MyClassTwoTest'.split(',');

List<ApexClass> classes = [SELECT Id, Name FROM ApexClass WHERE Name = :classNames];
if (classes.size() < classNames.size()) {
  Set<String> classSet = new Set<String>();
  List<String> invalidNames = new List<String>();
  for (ApexClass clz : classes) {
    classSet.add(clz.Name.toLowerCase());
  }
  for (String clz : classNames) {
    if (!classset.contains(clz.toLowerCase())) {
      invalidNames.add(clz);
    }
  }
  throw new CalloutException('One or more class names may be misspelled ' + String.join(invalidNames, ','));
}
// Id suiteId = '05FOy0000004b5pMAA';
HttpRequest request = new HttpRequest();
Http sender = new Http();
request.setHeader('Authorization', 'Bearer ' + UserInfo.getSessionID());
request.setHeader('Content-Type', 'application/json');
request.setMethod('POST');
request.setEndpoint(URL.getOrgDomainUrl() + '/services/data/v61.0/tooling/sobjects/ApexTestSuite/');
request.setBody('{"TestSuiteName": "' + suiteName + '"}');
HttpResponse resp = sender.send(request);
if (resp.getStatusCode() >= 300) {
  throw new CalloutException('Somethign went wrong ' + resp.getStatusCode() + ' ' + resp.getBody());
}
Map<String, Object> results = (Map<String, Object>) JSON.deserializeUntyped(resp.getBody());
if ((Boolean) results.get('success') == false) {
  throw new CalloutException('Somethign went wrong ' + resp.getBody());
}
Id suiteId = (Id) results.get('id');
request.setEndpoint(URL.getOrgDomainUrl() + '/services/data/v61.0/tooling/sobjects/TestSuiteMembership/');
for (ApexClass clz : classes) {
  Membership m = new Membership(suiteId, clz.Id);
  request.setBody(JSON.serialize(m));
  resp = sender.send(request);
  if (resp.getStatusCode() >= 300) {
    throw new CalloutException('Somethign went wrong ' + resp.getStatusCode() + ' ' + resp.getBody());
  }
  results = (Map<String, Object>) JSON.deserializeUntyped(resp.getBody());
  if ((Boolean) results.get('success') == false) {
    throw new CalloutException('Somethign went wrong ' + resp.getBody());
  }
}