Europe on Monday cheered Emmanuel Macron’s French presidential victory on a platform of a domestic economic overhaul and greater European integration, but it added a caveat: Show us that you mean it.

Mr. Macron has pledged to energize France’s drowsy economy with tough fiscal and labor market changes. But he also wants the 19 countries that use the euro to pool budget resources and Germany, the bloc’s heavyweight, to spend more to support the regional economy.

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