I am working on getting tests running in 10.14 as we are planning to upgrade our test infrastructure.

I found 3 tests in the mochitest-errata.ini file that I needed to comment out for a crash:
[generated/test_2_conformance__rendering__rendering-stencil-large-viewport.html]
[generated/test_2_conformance2__textures__misc__generate-mipmap-with-large-base-level.html]
[generated/test_2_conformance__canvas__drawingbuffer-static-canvas-test.html]

you can see the try jobs here:
https://treeherder.mozilla.org/#/jobs?repo=try&revision=f76caa997d7b6d7908ac0632bec21e3fbc94189f

and a log file:
https://taskcluster-artifacts.net/K6gORUu1T3uq5e8GID3-oA/0/public/logs/live_backing.log

The crash is on shutdown, so not at runtime, here is a clip from the log:
21:02:57 INFO - PROCESS-CRASH | Main app process exited normally | application crashed [@ mozilla::gl::MozFramebuffer::CreateWith(mozilla::gl::GLContext*, mozilla::gfx::IntSizeTyped<mozilla::gfx::UnknownUnits> const&, unsigned int, bool, unsigned int, unsigned int)]
21:02:57 INFO - Crash dump filename: /var/folders/g3/pns6yc6n3d1bcpfrrmp202j4000017/T/tmp52bB6B.mozrunner/minidumps/B21DC0BC-1268-4983-ACF9-B1060549BCAB.dmp
21:02:57 INFO - Operating system: Mac OS X
21:02:57 INFO - 10.14.0 18A391
21:02:57 INFO - CPU: amd64
21:02:57 INFO - family 6 model 69 stepping 1
21:02:57 INFO - 4 CPUs
21:02:57 INFO -
21:02:57 INFO - GPU: UNKNOWN
21:02:57 INFO -
21:02:57 INFO - Crash reason: EXC_BAD_ACCESS / KERN_INVALID_ADDRESS
21:02:57 INFO - Crash address: 0x0
21:02:57 INFO - Process uptime: 237 seconds
21:02:57 INFO -
21:02:57 INFO - Thread 0 (crashed)
21:02:57 INFO - 0 XUL!mozilla::gl::MozFramebuffer::CreateWith(mozilla::gl::GLContext*, mozilla::gfx::IntSizeTyped<mozilla::gfx::UnknownUnits> const&, unsigned int, bool, unsigned int, unsigned int) [MozFramebuffer.cpp:f76caa997d7b6d7908ac0632bec21e3fbc94189f : 131 + 0x29]
21:02:57 INFO - rax = 0x000000010b384a5c rdx = 0x0000000000000000
21:02:57 INFO - rcx = 0x0000000102e5c6a8 rbx = 0x0000000000008cdd
21:02:57 INFO - rsi = 0x00000000000120a8 rdi = 0x00007fff9ccbb028
21:02:57 INFO - rbp = 0x00007ffeed0c7480 rsp = 0x00007ffeed0c73e0
21:02:57 INFO - r8 = 0x00000000000130a8 r9 = 0x0000000000000000
21:02:57 INFO - r10 = 0x00007fff9ccbb048 r11 = 0x00007fff9ccbb040
21:02:57 INFO - r12 = 0x0000000000000000 r13 = 0x00000001478ef000
21:02:57 INFO - r14 = 0x000000011e9070a0 r15 = 0x00007ffeed0c7668
21:02:57 INFO - rip = 0x0000000104cbd4f7
21:02:57 INFO - Found by: given as instruction pointer in context
21:02:57 INFO - 1 XUL!mozilla::gl::MozFramebuffer::Create(mozilla::gl::GLContext*, mozilla::gfx::IntSizeTyped<mozilla::gfx::UnknownUnits> const&, unsigned int, bool) [MozFramebuffer.cpp:f76caa997d7b6d7908ac0632bec21e3fbc94189f : 68 + 0x7]
21:02:57 INFO - rbp = 0x00007ffeed0c7650 rsp = 0x00007ffeed0c7490
21:02:57 INFO - rip = 0x0000000104cbc6fe
21:02:57 INFO - Found by: previous frame's frame pointer
21:02:57 INFO - 2 XUL!mozilla::WebGLContext::EnsureDefaultFB() [WebGLContext.cpp:f76caa997d7b6d7908ac0632bec21e3fbc94189f : 649 + 0xb6]
21:02:57 INFO - rbp = 0x00007ffeed0c76a0 rsp = 0x00007ffeed0c7660
21:02:57 INFO - rip = 0x00000001066712c8
21:02:57 INFO - Found by: previous frame's frame pointer
21:02:57 INFO - 3 XUL!mozilla::WebGLContext::ValidateAndInitFB(mozilla::WebGLFramebuffer const*, unsigned int) [WebGLContext.cpp:f76caa997d7b6d7908ac0632bec21e3fbc94189f : 1744 + 0x5]
21:02:57 INFO - rbp = 0x00007ffeed0c76e0 rsp = 0x00007ffeed0c76b0
21:02:57 INFO - rip = 0x0000000106674a20
21:02:57 INFO - Found by: previous frame's frame pointer
21:02:57 INFO - 4 XUL!mozilla::WebGLContext::BindCurFBForDraw() [WebGLContext.cpp:f76caa997d7b6d7908ac0632bec21e3fbc94189f : 1771 + 0x11]
21:02:57 INFO - rbp = 0x00007ffeed0c7700 rsp = 0x00007ffeed0c76f0
21:02:57 INFO - rip = 0x0000000106675f4a
21:02:57 INFO - Found by: previous frame's frame pointer
21:02:57 INFO - 5 XUL!mozilla::ValidateDraw(mozilla::WebGLContext*, unsigned int, unsigned int) [WebGLContextDraw.cpp:f76caa997d7b6d7908ac0632bec21e3fbc94189f : 216 + 0x5]
21:02:57 INFO - rbp = 0x00007ffeed0c7760 rsp = 0x00007ffeed0c7710
21:02:57 INFO - rip = 0x000000010667bca0
21:02:57 INFO - Found by: previous frame's frame pointer