The "VDA Automotive SPICE Guidelines" (excerpts: https://vda-qmc.de/fileadmin/redakteur/Software/Automotive_SPICE/Veroeffentlichungen/VDA_Guideline_Rules_and_Recommendations_2017.xlsx) tells to lower the score "If the verification results (…) contain only a pure passed/failed information without a supporting verification log (…)"
What is sufficient to avoid the score being lowered for this reason?
I assume that the key point of interest is the "failed" part - the log must contain information on what failed, where, and why.
testID1: PASS testID2: FAIL at L1: var_1: expected X1, actual: A1 at L2: var_2: expected X2, actual: A2 testID3: PASS
 relevant, from the same guidelines: Test logs supplying a meaningful summary of the logged data as an adequate evidence for each test result. Sounds like "use common sense to determine what's enough".
[edit 2] I'd like a second opinion on logging PASSING checks (see discussion under Thomas' answer).
Aside from being of questionable use without the context (so, hardly a "meaningful summary"), they reduce the log's quality, with all the chaff. The test execution part alone, grows ~12 times, now being in tens of MBs. The log just doesn't feel like the right place for that.