-------------------------------------------------------------------------------
Test set: com.example.service.unit_testing.GeminiClientServiceTest
-------------------------------------------------------------------------------
Tests run: 5, Failures: 0, Errors: 5, Skipped: 0, Time elapsed: 0.495 s <<< FAILURE! -- in com.example.service.unit_testing.GeminiClientServiceTest
com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenUnexpectedExceptionOccurs_throwsGeminiClientException -- Time elapsed: 0.073 s <<< ERROR!
java.lang.NullPointerException: Cannot invoke "com.google.genai.Models.generateContent(String, com.google.genai.types.Content, com.google.genai.types.GenerateContentConfig)" because "this.geminiClient.models" is null
	at com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenUnexpectedExceptionOccurs_throwsGeminiClientException(GeminiClientServiceTest .java:115)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)

com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenGenAiIOExceptionOccurs_throwsGeminiClientException -- Time elapsed: 0.004 s <<< ERROR!
org.mockito.exceptions.misusing.InvalidUseOfMatchersException: 

Misplaced or misused argument matcher detected here:

-> at com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenUnexpectedExceptionOccurs_throwsGeminiClientException(GeminiClientServiceTest .java:115)
-> at com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenUnexpectedExceptionOccurs_throwsGeminiClientException(GeminiClientServiceTest .java:115)
-> at com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenUnexpectedExceptionOccurs_throwsGeminiClientException(GeminiClientServiceTest .java:115)

You cannot use argument matchers outside of verification or stubbing.
Examples of correct usage of argument matchers:
    when(mock.get(anyInt())).thenReturn(null);
    doThrow(new RuntimeException()).when(mock).someVoidMethod(any());
    verify(mock).someMethod(contains("foo"))

This message may appear after an NullPointerException if the last matcher is returning an object 
like any() but the stubbed method signature expect a primitive argument, in this case,
use primitive alternatives.
    when(mock.get(any())); // bad use, will raise NPE
    when(mock.get(anyInt())); // correct usage use

Also, this error might show up because you use argument matchers with methods that cannot be mocked.
Following methods *cannot* be stubbed/verified: final/private/equals()/hashCode().
Mocking methods declared on non-public parent classes is not supported.

	at com.example.service.unit_testing.GeminiClientServiceTest.setUp(GeminiClientServiceTest .java:50)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)

com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenResponseTextIsNull_throwsGeminiClientException -- Time elapsed: 0.404 s <<< ERROR!
java.lang.NullPointerException: Cannot invoke "com.google.genai.Models.generateContent(String, com.google.genai.types.Content, com.google.genai.types.GenerateContentConfig)" because "this.geminiClient.models" is null
	at com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenResponseTextIsNull_throwsGeminiClientException(GeminiClientServiceTest .java:87)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)

com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenApiSucceeds_returnsGeneratedText -- Time elapsed: 0.003 s <<< ERROR!
org.mockito.exceptions.misusing.InvalidUseOfMatchersException: 

Misplaced or misused argument matcher detected here:

-> at com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenResponseTextIsNull_throwsGeminiClientException(GeminiClientServiceTest .java:87)
-> at com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenResponseTextIsNull_throwsGeminiClientException(GeminiClientServiceTest .java:87)
-> at com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenResponseTextIsNull_throwsGeminiClientException(GeminiClientServiceTest .java:87)

You cannot use argument matchers outside of verification or stubbing.
Examples of correct usage of argument matchers:
    when(mock.get(anyInt())).thenReturn(null);
    doThrow(new RuntimeException()).when(mock).someVoidMethod(any());
    verify(mock).someMethod(contains("foo"))

This message may appear after an NullPointerException if the last matcher is returning an object 
like any() but the stubbed method signature expect a primitive argument, in this case,
use primitive alternatives.
    when(mock.get(any())); // bad use, will raise NPE
    when(mock.get(anyInt())); // correct usage use

Also, this error might show up because you use argument matchers with methods that cannot be mocked.
Following methods *cannot* be stubbed/verified: final/private/equals()/hashCode().
Mocking methods declared on non-public parent classes is not supported.

	at com.example.service.unit_testing.GeminiClientServiceTest.setUp(GeminiClientServiceTest .java:50)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)

com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenApiResponseIsNull_throwsGeminiClientException -- Time elapsed: 0.002 s <<< ERROR!
java.lang.NullPointerException: Cannot invoke "com.google.genai.Models.generateContent(String, com.google.genai.types.Content, com.google.genai.types.GenerateContentConfig)" because "this.geminiClient.models" is null
	at com.example.service.unit_testing.GeminiClientServiceTest.generateContent_whenApiResponseIsNull_throwsGeminiClientException(GeminiClientServiceTest .java:72)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)