[BUG] Generation of test cases are failing for spring.

OpenAPI generator is not generating Integration test cases for spring API's
Using the following generator to generate spring based code from openAPI specification.
<openapi-generator-maven-plugin.version>4.0.2</openapi-generator-maven-plugin.version>
swagger spec
https://github.com/OAI/OpenAPI-Specification/blob/master/examples/v3.0/petstore.yaml

However, older swagger-codegen is able to generate integration test cases for API's.

1#Code generation using openapi-generator 4.0.2
rm -rf Tester/* && openapi-generator generate -i petstore.yaml -g spring --library spring-mvc -o Tester/
skhedkar@Thanos:~/sandbox/trunk/jhipster$ tree Tester/
Tester/
├── pom.xml
├── README.md
└── src
└── main
├── java
│   └── org
│   └── openapitools
│   ├── api
│   │   ├── ApiUtil.java
│   │   ├── PetsApiController.java
│   │   └── PetsApi.java
│   ├── configuration
│   │   ├── HomeController.java
│   │   ├── OpenAPIDocumentationConfig.java
│   │   ├── OpenAPIUiConfiguration.java
│   │   ├── RFC3339DateFormat.java
│   │   ├── WebApplication.java
│   │   └── WebMvcConfiguration.java
│   └── model
│   ├── Error.java
│   └── Pet.java
└── resources
└── application.properties

9 directories, 14 files

2#Code generation using swagger-codegen-cli 3.0.9
rm -rf Tester/* && java -jar swagger-codegen-cli-3.0.9-20190627.154813-43.jar generate -i petstore.yaml -l spring --library spring-mvc -o Tester/

skhedkar@Thanos:~/sandbox/trunk/swagger$ tree Tester/
Tester/
├── pom.xml
├── README.md
└── src
├── main
│   ├── java
│   │   └── io
│   │   └── swagger
│   │   ├── api
│   │   │   ├── ApiException.java
│   │   │   ├── ApiOriginFilter.java
│   │   │   ├── ApiResponseMessage.java
│   │   │   ├── NotFoundException.java
│   │   │   ├── PetsApiController.java
│   │   │   └── PetsApi.java
│   │   ├── configuration
│   │   │   ├── CustomInstantDeserializer.java
│   │   │   ├── RFC3339DateFormat.java
│   │   │   ├── SwaggerDocumentationConfig.java
│   │   │   ├── SwaggerUiConfiguration.java
│   │   │   ├── WebApplication.java
│   │   │   └── WebMvcConfiguration.java
│   │   └── model
│   │   ├── Error.java
│   │   ├── Pet.java
│   │   └── Pets.java
│   └── resources
│   └── swagger.properties
└── test
└── java
└── io
└── swagger
└── api
└── PetsApiControllerIT.java

Major difference between openapi-generator and swagger-codegen-cli is that template file api_test.mustache is missing in former.

https://github.com/OpenAPITools/openapi-generator/tree/v4.0.2/modules/openapi-generator/src/main/resources/JavaSpring/libraries/spring-mvc

https://github.com/swagger-api/swagger-codegen/tree/master/modules/swagger-codegen/src/main/resources/JavaSpring/libraries/spring-mvc

I don't know if it is a bug or test case generation is not supported for spring in openapi-generator.

Start with the JavaSpring spring-mvc templates under modules/openapi-generator/src/main/resources/JavaSpring/libraries/spring-mvc and compare them with the linked swagger-codegen templates, especially api_test.mustache. Reproduce generation with petstore.yaml and openapi-generator 4.0.2, then verify that the generated project includes the expected integration test under src/test and that it can run.