UnexpectedExceptionTests should tolerate Mono on Azure DevOps Ubuntu

[jnm2]

The Linux build failed on all the Mono tests:

1) Failed : NUnit.Framework.Internal.UnexpectedExceptionTests.FailRecordsInnerExceptionsAsPartOfAggregateException
  Expected string length 153 but was 203. Strings differ at index 53.
  Expected: "...on : Outer Aggregate Exception\n  ----> System.Exception : ..."
  But was:  "...on : Outer Aggregate Exception (Inner Exception 1 of 2) (I..."
  --------------------------------------------^
  at NUnit.Framework.Internal.UnexpectedExceptionTests.FailRecordsInnerExceptionsAsPartOfAggregateException () [0x0005e] in <2086766ee22743e488729c0438b8b918>:0 

2) Failed : NUnit.Framework.Internal.UnexpectedExceptionTests.FailRecordsNestedInnerExceptionAsPartOfAggregateException
  Expected string length 145 but was 163. Strings differ at index 53.
  Expected: "...on : Outer Aggregate Exception\n  ----> System.Exception : ..."
  But was:  "...on : Outer Aggregate Exception (Inner Exception)\n  ----> S..."
  --------------------------------------------^
  at NUnit.Framework.Internal.UnexpectedExceptionTests.FailRecordsNestedInnerExceptionAsPartOfAggregateException () [0x0005e] in <2086766ee22743e488729c0438b8b918>:0 

https://nunit.visualstudio.com/NUnit/_build/results?buildId=1308&view=logs&jobId=0da5d1d9-276d-5173-c4c4-9d4d4ed14fdb&taskId=8ef82b3b-1feb-5bbd-06f6-b1f7b5467f03&lineStart=708&lineEnd=720&colStart=1&colEnd=196

These tests need to be made less specific so that they tolerate platform differences.

[mikkelbu]

Looks like it behaves like the case for NETCOREAPP1_1 || NETCOREAPP2_0 in the code. What if we changed the assertion to assert that:

• The message starts with System.AggregateException : Outer Aggregate Exception
• The message ends with

"  ----> System.Exception : Inner Exception 1 of 2" + Environment.NewLine +
"  ----> System.Exception : Inner Exception 2 of 2";

[jnm2]

@mikkelbu That sounds good.