I'm using:
Spring Tool Suite 4 Version: 4.4.2.RELEASE Build Id: 201911201053 Java version: 1.8.0_191
and the message displayed is No tests found with test runner 'JUnit5'
what worked for me was the configuration below
<properties>
<java.version>1.8</java.version>
<junit-jupiter.version>5.5.2</junit-jupiter.version>
<junit-platform.version>1.5.2</junit-platform.version>
</properties>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-engine</artifactId>
<version>${junit-jupiter.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.junit.platform</groupId>
<artifactId>junit-platform-launcher</artifactId>
<version>${junit-platform.version}</version>
<scope>test</scope>
</dependency>