With VMware Workstation 14.1.2, buffer is on by default now. Please try WS14.1.2, and also let us know if it fixes your last issue about your test-suite.
Today I upgraded to VMware Workstation Player 15.0.3 (original version was 12.5.8) and I immediately noticed that VMs were trashing my host system's memory cache. Of course it's cool that VMs benefit of greatly increased IO performance with memory cache enabled, but I wasn't amazed that this is automatically enabled by default - most notably without any warning or hint. I haven't found any changelog that mentions this, only this well hidden forum post. So, funnily enough, I can confirm that this change works. However, the unwanted side effect is that it's enabled for everything - according to the experience I made. In order to disable this, I added a line called hard-disk.hostBuffer = "disabled" to "C:\ProgramData\VMware\VMware Workstation\config.ini". Now it's globally disabled, but I have seen it works to enable this for specific VMs by adding disk.hostBuffer = "enabled" in the vmx file for each VM respectively.
Please be more transparent with such changes for upcoming newer versions. Thank you!