Fix test suite

[fingolfin]

Tests are failing in all tested Julia versions. E.g. in this log with Julia 1.6

┌ Error: Divergence in chunk starting at index 1994103
│   chunk =
│    16384-element view(::Vector{UInt8}, 1:16384) with eltype UInt8:
│     0x16
│     0xc0
│        ⋮
│     0x75
│   truth_chunk =
│    7421-element Vector{UInt8}:
│     0x16
│     0xc0
│        ⋮
│     0x46
└ @ Main ~/work/SimpleBufferStream.jl/SimpleBufferStream.jl/test/runtests.jl:215

Running the tests on my own machine in Julia 1.9 I see this:

┌ Error: Divergence in chunk starting at index 1998001
│   chunk =
│    1024-element view(::Vector{UInt8}, 1:1024) with eltype UInt8:
│     0x2f
│     0xc6
│     0xff
│     0xdd
│     0xa1
│     0xfc
│     0x7f
│     0xe7
│        ⋮
│     0x7f
│     0xd8
│     0xcd
│     0xff
│     0x05
│     0x9c
│     0xf6
│   truth_chunk =
│    202-element Vector{UInt8}:
│     0x2f
│     0xc6
│     0xff
│     0xdd
│     0xa1
│     0xfc
│     0x7f
│     0xe7
│        ⋮
│     0x99
│     0x6d
│     0xb2
│     0xfe
│     0x33
│     0xc2
│     0xff
└ @ Main ~/Projekte/Julia/packages/JuliaPackaging/SimpleBufferStream.jl/test/runtests.jl:215

Running them in GH Actions CI with Julia 1.9, we see:

Test Failed at /home/runner/work/SimpleBufferStream.jl/SimpleBufferStream.jl/test/runtests.jl:16
  Expression: t_elapsed > 0.01
   Evaluated: 0.006773171 > 0.01

basic usage: Error During Test at /home/runner/work/SimpleBufferStream.jl/SimpleBufferStream.jl/test/runtests.jl:21
  Test threw exception
  Expression: fetch(t_read) == "go"
  TaskFailedException
  Stacktrace:
   [1] wait
     @ ./task.jl:349 [inlined]
   [2] fetch(t::Task)
     @ Base ./task.jl:369
   [3] macro expansion
     @ /opt/hostedtoolcache/julia/1.9.0/x64/share/julia/stdlib/v1.9/Test/src/Test.jl:478 [inlined]
   [4] macro expansion
     @ ~/work/SimpleBufferStream.jl/SimpleBufferStream.jl/test/runtests.jl:21 [inlined]
   [5] macro expansion
     @ /opt/hostedtoolcache/julia/1.9.0/x64/share/julia/stdlib/v1.9/Test/src/Test.jl:1498 [inlined]
   [6] top-level scope
     @ ~/work/SimpleBufferStream.jl/SimpleBufferStream.jl/test/runtests.jl:4
  
      nested task error: There was an error during testing