TaskCollectionVisitPrefetcher.diff

public function findUpcomingForPatient(Patient $patient): ?Visit
{
-    return $this->cache->fetch($patient->getId())
-        ?: $this->visits->findUpcomingForPatient($patient);
+    $key = $patient->getId();
+    if ($this->cache->contains($key)) {
+        return $this->cache->fetch($key);
+    }
+
+    return $this->visits->findUpcomingForPatient($patient);
}

TaskCollectionVisitPrefetcherTest.php

<?php 

public function repository call is prevented if the cache contains a null value()
{
    // given …
    // when:
    $sut->prefetch($this->task);
    // then:
    $visits
        ->expects(self::never())
        ->method('findUpcomingForPatient');

    $sut->findUpcomingForPatient($this->patient);
}