Update testing-with-corefx.md

Clarify the way the `BUILDTOOLS_OVERRIDE_RUNTIME` option is passed.

1 files changed, 5 insertions, 1 deletions

diff --git a/Documentation/building/testing-with-corefx.md b/Documentation/building/testing-with-corefx.md
index 6609a0aaa7..4f9886f78d 100644
--- a/Documentation/building/testing-with-corefx.md
+++ b/Documentation/building/testing-with-corefx.md
@@ -7,7 +7,11 @@ It may be valuable to use CoreFX tests to validate your changes to CoreCLR or ms
 
 As part of building tests, CoreFX restores a copy of the runtime from myget, in order to update the runtime that is deployed, a special build property `BUILDTOOLS_OVERRIDE_RUNTIME` can be used. If this is set, the CoreFX testing targets will copy all the files in the folder it points to into the test folder, overwriting any files that exist.
 
-To run tests, follow the procedure for [running tests in CoreFX](https://github.com/dotnet/corefx/blob/master/Documentation/building/windows-instructions.md). You can pass `/p:BUILDTOOLS_OVERRIDE_RUNTIME=<path-to-coreclr>\bin\Product\Windows_NT.x64.Release` to build.cmd to set this property.
+To run tests, follow the procedure for [running tests in CoreFX](https://github.com/dotnet/corefx/blob/master/Documentation/building/windows-instructions.md). You can pass `/p:BUILDTOOLS_OVERRIDE_RUNTIME=<path-to-coreclr>\bin\Product\Windows_NT.x64.Release` to build.cmd to set this property, e.g. (note the space between the "--" and the "/p" option):
+
+```
+build.cmd -Release -- /p:BUILDTOOLS_OVERRIDE_RUNTIME=<root of coreclr repo>\bin\Product\Windows_NT.x64.Checked
+```
 
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