You can clone with
sprintf tests on rounding numbers like 1.969.
Tests issues found by japhb.
Add more tests for Inf and -Inf.
These tests follow the Perl 5 convention. I'm not convinced of
its correctness. I also changed two existing tests to conform.
Test FatRat with %d.
Unfudge tests in JVM.
Unfudge for Rakudo.jvm.
Add simple %x test that would have prevented my last nieczabug.
Add tests for default precision in floating point formats.
Lots more sprintf tests. But we could still use even more!
Add a bare minimum of tests for %e, %E, %f, %F, %g, and %G.
More tests here are definitely needed.