Mockito.mockStatic always returns null

Question

I am trying to mock static method which always returns null.

try (MockedStatic<SecretsUtility> utilityMockedStatic = Mockito.mockStatic(SecretsUtility.class)) {
            utilityMockedStatic.when(() -> SecretsUtility.readSecret(Mockito.anyString())).thenReturn("abc");
        }

static method

public String readSecret(String secretPath)
            throws SFEventProcessException {

        try (FileInputStream fin = new FileInputStream(secretPath)) {

            return secretValue;
        } catch (IOException ex) {
            throw new Exception(ex.getMessage());
        }
    }

I am not able to see secretPath while debugging, it says cannot find local variable secretPath.