PerformanceTestExecution results = sortedExecutions.get(index);
            MeasuredOperationList baselineVersion = results.getScenarios().get(testHistory.getScenarioLabels().indexOf(label));
            MeasuredOperationList currentVersion = results.getScenarios().get(testHistory.getScenarioLabels().size() - 1);
            return baselineVersion.isEmpty() ? null : Arrays.asList(index, dataExtractor.apply(baselineVersion, currentVersion));

        return ImmutableList.of();
    }

    @Override
    public int getScenarioCount() {
        return 0;
    }

    @Override
    public List<String> getScenarioLabels() {
        return ImmutableList.of();
    }

    @Override
    public List<? extends ScenarioDefinition> getScenarios() {
        return ImmutableList.of();
    }

     * Returns the number of scenarios for this performance test.
     */
    int getScenarioCount();

    /**
     * Returns the display names for the scenarios of this performance test.
     */
    List<String> getScenarioLabels();

    /**
     * Returns the scenarios that are executed for this performance test.
     */
    List<? extends ScenarioDefinition> getScenarios();

    }

    @Override
    public int getScenarioCount() {
        return builds.size();
    }

    @Override
    public List<String> getScenarioLabels() {
        return Lists.transform(builds, BuildDisplayInfo::getDisplayName);
    }

    @Override
    public List<? extends ScenarioDefinition> getScenarios() {
        return builds.stream()

            .collect(Collectors.toList());
    }

    @Override
    public int getScenarioCount() {
        return getKnownVersions().size();
    }

    @Override
    public List<String> getScenarioLabels() {
        return getKnownVersions();
    }

    private class KnownVersionsPerformanceTestExecution implements PerformanceTestExecution {
        private final CrossVersionPerformanceResults result;

            end();
            tr();
            th().text("Date").end();
            th().text("Branch").end();
            th().text("Git commit").end();
            for (String label : testHistory.getScenarioLabels()) {
                renderHeaderForSamples(label);
            }
            th().text("Confidence").end();
            th().text("Difference").end();
            th().text("Test version").end();