diff --git a/tests-execution-chart-commons/src/test/groovy/io/github/platan/tests_execution_chart/reporters/json/JsonReporterTest.groovy b/tests-execution-chart-commons/src/test/groovy/io/github/platan/tests_execution_chart/reporters/json/JsonReporterTest.groovy
index 6f271d5..f55821e 100644
--- a/tests-execution-chart-commons/src/test/groovy/io/github/platan/tests_execution_chart/reporters/json/JsonReporterTest.groovy
+++ b/tests-execution-chart-commons/src/test/groovy/io/github/platan/tests_execution_chart/reporters/json/JsonReporterTest.groovy
@@ -1,8 +1,6 @@
 package io.github.platan.tests_execution_chart.reporters.json
 
-import io.github.platan.tests_execution_chart.report.data.Mark
-import io.github.platan.tests_execution_chart.report.data.TestExecutionScheduleReport
-import io.github.platan.tests_execution_chart.report.data.TimedTestResult
+import io.github.platan.tests_execution_chart.report.TestExecutionScheduleReportBuilder
 import spock.lang.Specification
 import spock.lang.TempDir
 
@@ -18,9 +16,9 @@ class JsonReporterTest extends Specification {
     def "should generate report in json"() {
         given:
         def configOutputLocation = "my-output-location"
-        def report = new TestExecutionScheduleReport([
-                new TimedTestResult('class', 'test', toEpochMilli('2023-03-10T19:00:02Z'), toEpochMilli('2023-03-10T19:00:05Z'), 'passed', TEST)
-        ], [new Mark('mark1', toEpochMilli('2023-03-10T19:00:05Z'))])
+        def report = new TestExecutionScheduleReportBuilder()
+                .addResult('class', 'test', toEpochMilli('2023-03-10T19:00:02Z'), toEpochMilli('2023-03-10T19:00:05Z'), 'passed', TEST)
+                .addMark('mark1', toEpochMilli('2023-03-10T19:00:05Z')).build()
         def reporter = new JsonReporter().tap {
             it.setConfiguration(new JsonConfig(true, configOutputLocation))
         }
diff --git a/tests-execution-chart-commons/src/test/groovy/io/github/platan/tests_execution_chart/reporters/mermaid/MermaidTestsReporterTest.groovy b/tests-execution-chart-commons/src/test/groovy/io/github/platan/tests_execution_chart/reporters/mermaid/MermaidTestsReporterTest.groovy
new file mode 100644
index 0000000..9c152b2
--- /dev/null
+++ b/tests-execution-chart-commons/src/test/groovy/io/github/platan/tests_execution_chart/reporters/mermaid/MermaidTestsReporterTest.groovy
@@ -0,0 +1,48 @@
+package io.github.platan.tests_execution_chart.reporters.mermaid
+
+import io.github.platan.tests_execution_chart.report.TestExecutionScheduleReportBuilder
+import spock.lang.Specification
+import spock.lang.Subject
+import spock.lang.TempDir
+
+import java.time.Instant
+
+import static io.github.platan.tests_execution_chart.report.data.TimedTestResult.Type.TEST
+
+class MermaidTestsReporterTest extends Specification {
+
+    @TempDir
+    File baseDir
+
+    def configOutputLocation = "my-output-location"
+
+    @Subject
+    def reporter = new MermaidTestsReporter().tap {
+        it.setConfiguration(new MermaidConfig(true, configOutputLocation))
+    }
+
+    def "should generate report in mermaid format"() {
+        given:
+        def report = new TestExecutionScheduleReportBuilder()
+                .addResult('class', 'test', toEpochMilli('2023-03-10T19:00:02Z'), toEpochMilli('2023-03-10T19:00:05Z'), 'passed', TEST)
+                .addMark('mark1', toEpochMilli('2023-03-10T19:00:05Z')).build()
+
+        when:
+        reporter.report(report, baseDir, "taskname")
+
+        then:
+        def reportFile = new File(baseDir, "$configOutputLocation/taskname.txt")
+        reportFile.text ==
+                """|gantt
+                |dateFormat YYYY-MM-DDTHH:mm:ss.SSSZZ
+                |axisFormat %H:%M:%S.%L
+                |section class
+                |test - 3000 ms :2023-03-10T20:00:02.000+0100, 2023-03-10T20:00:05.000+0100
+                |mark1 : milestone, 2023-03-10T20:00:05.000+0100, 0
+                |""".stripMargin()
+    }
+
+    private static long toEpochMilli(String instant) {
+        Instant.parse(instant).toEpochMilli()
+    }
+}