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// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CHROME_TEST_BASE_WEB_FEATURE_HISTOGRAM_TESTER_H_
#define CHROME_TEST_BASE_WEB_FEATURE_HISTOGRAM_TESTER_H_
#include <map>
#include <vector>
#include "base/test/metrics/histogram_tester.h"
#include "third_party/blink/public/mojom/use_counter/metrics/web_feature.mojom.h"
// Returns a map containing the given `features` as keys, all mapping to zero.
std::map<blink::mojom::WebFeature, int> AllZeroFeatureCounts(
const std::vector<blink::mojom::WebFeature>& features);
// Builds a new map by adding the value in `lhs` and `rhs` key-wise.
//
// Useful in conjunction with `AllZeroFeatureCounts()`, when building a map of
// mostly zero values with a few exceptions.
std::map<blink::mojom::WebFeature, int> AddFeatureCounts(
const std::map<blink::mojom::WebFeature, int>& lhs,
const std::map<blink::mojom::WebFeature, int>& rhs);
// Helper for testing `WebFeature` use counts recorded as UMA histograms.
//
// Wraps around `base::HistogramTester` and provides a simpler API centered
// around `WebFeature`s. Similarly to `base::HistogramTester`, the counts
// returned by this instance are relative diffs compared to the histogram
// values at construction time.
//
// This class publicly depends solely on content/ code, yet it is defined in
// chrome/ on purpose. Indeed, `WebFeature` use counts are recorded in UMA
// histograms by components/page_load_metrics, which sits above content/. While
// this code may compile in content/, content/ tests written against it would
// observe zero counts that never increase, because no code would be recording
// the feature use counts in histograms.
class WebFeatureHistogramTester final {
public:
// Takes a snapshot of counts.
WebFeatureHistogramTester();
WebFeatureHistogramTester(const WebFeatureHistogramTester&) = delete;
WebFeatureHistogramTester& operator=(const WebFeatureHistogramTester&) =
delete;
~WebFeatureHistogramTester();
// Returns the current count of the given `feature`.
// This is a diff from the snapshot taken at construction time.
int GetCount(blink::mojom::WebFeature feature) const;
// Returns a map of the given `features` to their corresponding count.
// These are diffs from the snapshot taken at construction time.
// Duplicate features are ignored.
std::map<blink::mojom::WebFeature, int> GetCounts(
const std::vector<blink::mojom::WebFeature>& features) const;
// Same as `GetCounts()`, except that entries with zero counts are skipped.
std::map<blink::mojom::WebFeature, int> GetNonZeroCounts(
const std::vector<blink::mojom::WebFeature>& features) const;
// Waits for the given features' counts to reach the `expected` values, then
// returns the last observed feature counts.
//
// `expected` must have only non-negative values.
//
// As with other methods above, `expected` is compared against diffs from
// the snapshot taken at constructon time.
//
// See also `AllZeroFeatureCounts()` and `AddFeatureCounts()` for help
// building `expected`.
std::map<blink::mojom::WebFeature, int> WaitForCountsAtLeast(
const std::map<blink::mojom::WebFeature, int>& expected) const;
// Equivalent to `EXPECT_EQ(WaitForCountsAtLeast(expected), expected)`.
void ExpectCounts(
const std::map<blink::mojom::WebFeature, int>& expected) const;
private:
int GetCountInternal(blink::mojom::WebFeature feature) const;
std::map<blink::mojom::WebFeature, int> GetCountsInternal(
const std::vector<blink::mojom::WebFeature>& features,
bool include_zeroes) const;
base::HistogramTester histogram_tester_;
};
#endif // CHROME_TEST_BASE_WEB_FEATURE_HISTOGRAM_TESTER_H_
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