diff --git a/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/assertions/logAssertions.kt b/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/assertions/logAssertions.kt
index 5400cbb36e6..30e43b8340e 100644
--- a/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/assertions/logAssertions.kt
+++ b/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/assertions/logAssertions.kt
@@ -14,7 +14,7 @@ fun CompilationOutcome.assertLogContainsLines(logLevel: LogLevel, vararg expecte
 
 fun CompilationOutcome.assertLogContainsLines(logLevel: LogLevel, expectedLines: Set<String>) {
     requireLogLevel(logLevel)
-    val absentLines = expectedLines.filter { !logLines.getValue(logLevel).contains(it) }
+    val absentLines = expectedLines.filter { !uniqueLogLines.getValue(logLevel).contains(it) }
     assert(absentLines.isEmpty()) {
         """
         |The following lines were expected to be printed on $logLevel level, however they were not:
@@ -29,7 +29,7 @@ fun CompilationOutcome.assertLogDoesNotContainLines(logLevel: LogLevel, vararg e
 
 fun CompilationOutcome.assertLogDoesNotContainLines(logLevel: LogLevel, expectedLines: Set<String>) {
     requireLogLevel(logLevel)
-    val presentLines = expectedLines.filter { logLines.getValue(logLevel).contains(it) }
+    val presentLines = expectedLines.filter { uniqueLogLines.getValue(logLevel).contains(it) }
     assert(presentLines.isEmpty()) {
         """
         |The following lines were not expected to be printed on $logLevel level, however they were:
diff --git a/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/model/AbstractModule.kt b/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/model/AbstractModule.kt
index 48e16d2a263..b8d13ef55dc 100644
--- a/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/model/AbstractModule.kt
+++ b/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/model/AbstractModule.kt
@@ -12,8 +12,22 @@ import org.junit.jupiter.api.Assertions.assertEquals
 import java.nio.file.Path
 
 private class CompilationOutcomeImpl(
-    override val logLines: Map<LogLevel, Collection<String>>,
+    rawLogLines: Map<LogLevel, Collection<String>>,
 ) : CompilationOutcome {
+    private val _logLines by lazy {
+        rawLogLines.mapValues { (_, lines) -> lines.toList() }
+    }
+
+    override val logLines: Map<LogLevel, List<String>>
+        get() = _logLines
+
+    private val _uniqueLogLines by lazy {
+        rawLogLines.mapValues { (_, lines) -> lines.toSet() }
+    }
+
+    override val uniqueLogLines: Map<LogLevel, Set<String>>
+        get() = _uniqueLogLines
+
     var maxLogLevel: LogLevel = LogLevel.ERROR
         private set
     var expectedResult = CompilationResult.COMPILATION_SUCCESS
diff --git a/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/model/CompilationOutcome.kt b/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/model/CompilationOutcome.kt
index 45402f5a488..897613dc197 100644
--- a/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/model/CompilationOutcome.kt
+++ b/compiler/build-tools/kotlin-build-tools-api-tests/src/main/kotlin/compilation/model/CompilationOutcome.kt
@@ -8,7 +8,9 @@ package org.jetbrains.kotlin.buildtools.api.tests.compilation.model
 import org.jetbrains.kotlin.buildtools.api.CompilationResult
 
 interface CompilationOutcome {
-    val logLines: Map<LogLevel, Collection<String>>
+    val logLines: Map<LogLevel, List<String>>
+
+    val uniqueLogLines: Map<LogLevel, Set<String>>
 
     fun requireLogLevel(logLevel: LogLevel)