[NPE] Checking if HealthCheck exists before tryin to perform it

Author: jlannoy

src/main/java/net/zileo/ohdear/healthchecks/service/HealthCheckRegistry.java

@@ -49,6 +49,9 @@ public CheckResultsHolder performAll() {
     }
 
     public CheckResultsHolder perform(String healthCheckName) {
+        if (!this.healthChecks.containsKey(healthCheckName)) {
+            throw new IllegalArgumentException("No health check with name '" + healthCheckName + "' has been registered");
+        }
         CheckResultsHolder results = new CheckResultsHolder();
         results.addCheckResult(perform(this.healthChecks.get(healthCheckName)));
         results.setFinishedDate(new Date());

src/test/java/net/zileo/ohdear/healthchecks/service/HealthCheckRegistryTest.java

@@ -160,6 +160,18 @@ void testCustomHealthCheck() {
         assertCustomHealthCheckResult(results.getCheckResults().get(0));
     }
 
+    @Test
+    void testMissingRegisteredHealthCheck() {
+        final String name = "NotExistingHealthCheck";
+
+        IllegalArgumentException exception = Assertions.assertThrows(IllegalArgumentException.class, () -> {
+            HealthCheckRegistry r = new HealthCheckRegistry();
+            r.perform("NotExistingHealthCheck");
+        });
+
+        Assertions.assertTrue(exception.getMessage().contains(name));
+    }
+
     private void assertCustomHealthCheckResult(CheckResult result) {
         assertResult(result, HealthCheckStatus.OK, CustomResultHealthCheck.NAME, CustomResultHealthCheck.LABEL, CustomResultHealthCheck.SUMMARY, CustomResultHealthCheck.MESSAGE, List.of("meta", "tag", "meta2", "tag2"));
     }