title: openapi-generator-maven-plugin not generating any test cases when the provided generatorName is spring
body: <p>I have an api.yml file which i used to generate restendpoint using maven generte-sources command
  The source got generated in target/generated-sources but no test cases are being generated.</p>
  
  <p>I have tried setting false but nothing happened</p>
  
  <p>my configuration is here</p>
  
  <pre><code> &lt;plugin&gt;
  &lt;groupId&gt;org.openapitools&lt;/groupId&gt;
  &lt;artifactId&gt;openapi-generator-maven-plugin&lt;/artifactId&gt;
  &lt;version&gt;4.0.0&lt;/version&gt;
  &lt;executions&gt;
      &lt;execution&gt;        
          &lt;goals&gt;
              &lt;goal&gt;generate&lt;/goal&gt;
          &lt;/goals&gt;
          &lt;configuration&gt;
              &lt;inputSpec&gt;${project.basedir}\src\main\resources\api.yml&lt;/inputSpec&gt;
              &lt;modelPackage&gt;com.demo.model&lt;/modelPackage&gt;
              &lt;apiPackage&gt;com.demo.api&lt;/apiPackage&gt;
              &lt;generatorName&gt;spring&lt;/generatorName&gt;
              &lt;supportingFilesToGenerate&gt;ApiUtil.java&lt;/supportingFilesToGenerate&gt;
                  &lt;generateApi&gt;True&lt;/generateApi&gt;
                  &lt;generateApiTests&gt;True&lt;/generateApiTests&gt;
                  &lt;generateModelTests&gt;True&lt;/generateModelTests&gt;
                  &lt;validateSpec&gt;true&lt;/validateSpec&gt;
                  &lt;configOptions&gt;
                   &lt;delegatePattern&gt;true&lt;/delegatePattern&gt;
                   &lt;title&gt;swagger-codegen-demo&lt;/title&gt;
              &lt;/configOptions&gt;
          &lt;/configuration&gt;
       &lt;/execution&gt;
  
  &lt;/executions&gt;
  </code></pre>
  
  <p></p>