[MESOS-7877] Audit test code for undefined behavior in accessing container elements

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 1.5.0
• Component/s: test
• Labels: mesosphere newbie tech-debt test
• Sprint: Mesosphere Sprint 62, Mesosphere Sprint 63, Mesosphere Sprint 64, Mesosphere Sprint 65
• Story Points: 2
• Assignee: Gastón Kleiman
• Reporter: Benjamin Bannier
• Created: 10/Aug/17 10:15
• Updated: 26/Mar/18 21:03
• Resolved: 05/Oct/17 19:10

Description

We do not always make sure we never access elements from empty containers, e.g., we use patterns like the following

Future<vector<Offer>> offers;

// Satisfy offers.

EXPECT_FALSE(offers.empty());

const auto& offer = (*offers)[0];

While the intention here is to diagnose an empty offers, the code still exhibits undefined behavior in the element access if offers was indeed empty (compilers might aggressively exploit undefined behavior to e.g., remove "impossible" code). Instead one should prevent accessing any elements of an empty container, e.g.,

ASSERT_FALSE(offers.empty()); // Prevent execution of rest of test body.

We should audit and fix existing test code for such incorrect checks and variations involving e.g., EXPECT_NE.