diff --git a/eo-maven-plugin/src/test/java/org/eolang/maven/UnphiMojoTest.java b/eo-maven-plugin/src/test/java/org/eolang/maven/UnphiMojoTest.java
index df66a71040..3316cb2f96 100644
--- a/eo-maven-plugin/src/test/java/org/eolang/maven/UnphiMojoTest.java
+++ b/eo-maven-plugin/src/test/java/org/eolang/maven/UnphiMojoTest.java
@@ -112,10 +112,12 @@ void convertsToXmirAndBack(final String pack, @TempDir final Path temp) throws E
             .result()
             .get(main);
         MatcherAssert.assertThat(
+            String.format("%s should have been rewritten after optimization, but it wasn't", main),
             result.toFile().lastModified(),
             Matchers.greaterThan(saved)
         );
         MatcherAssert.assertThat(
+            "Origin phi should equal to phi got from \"unphied\" xmir, but it isn't",
             phi,
             Matchers.equalTo(
                 new TextOf(result).asString()