[BUG] Kotlin spring reactive api test invalid

Created by: Zomzog

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

When generating API with array response, Flow import is missing on API tests.

Test also need runBlockingTest to handle suspend functions.

openapi-generator version

4.0.2-SNAPSHOT

OpenAPI declaration file content or url

      responses:
        200:
          description: "Status 200"
          content:
            application/json:
              schema:
                type: "array"
                items:
                  type: "string"

Command line used for generation

            <plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <version>4.0.2-SNAPSHOT</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>${project.basedir}/src/main/resources/api.yaml</inputSpec>
                            <generatorName>kotlin-spring</generatorName>
                            <library>spring-boot</library>
                            <configOptions>
                                <reactive>true</reactive>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

Related issues/PRs

Suggest a fix

Add import and runBlockingTest.