intellij-plugin/educational-core/testResources/META-INF/plugin.xml

<idea-plugin xmlns:xi="http://www.w3.org/2001/XInclude">
  <id>com.jetbrains.edu.core</id>
  <xi:include href="/META-INF/educational-core.xml" xpointer="xpointer(/idea-plugin/*)"/>

  <extensions defaultExtensionNs="com.intellij">
    <fileType language="FakeGradleBasedLanguage"
              name="FakeGradleFileType"
              extensions="kt"
              implementationClass="com.jetbrains.edu.learning.configurators.FakeGradleFileType"/>
    <fileType language="FakeBinaryDBFileType"
              name="FakeDBFileType"
              extensions="db"
              implementationClass="com.jetbrains.edu.learning.stepik.hyperskill.FakeBinaryDBFileType"/>
  </extensions>
</idea-plugin>