Make maximum buffer size of TestCase configurable

This removes the global variable `BUFFER_SIZE` in favor of a new field
in `CheckConfig`.

Closes #17

Author: Seelengrab

src/teststate.jl

@@ -261,13 +261,6 @@ function target!(ts::TestState)
     end
 end
 
-"""
-    BUFFER_SIZE
-
-The default maximum buffer size to use for a test case.
-"""
-const BUFFER_SIZE = Ref((100 * 1024) % UInt)
-
 """
     generate(ts::TestState)
 
@@ -288,7 +281,7 @@ function generate!(ts::TestState)
             (isnothing(ts.best_scoring) || # no score
              (ts.valid_test_cases <= ts.config.max_examples÷2))
         # +1, since we this test case is for the *next* call
-        tc = TestCase(UInt64[], ts.rng, ts.calls+1, ts.config.max_examples, BUFFER_SIZE[])
+        tc = TestCase(UInt64[], ts.rng, ts.calls+1, ts.config.max_examples, ts.config.buffer_size*8)
         test_function(ts, tc)
     end
 end

src/types.jl

@@ -75,6 +75,15 @@ Fields:
  * `record`: Whether the result should be recorded in the parent testset, if there is one
  * `verbose`: Whether the printing should be verbose, i.e. print even if it's a `Pass`
  * `broken`: Whether the invocation is expected to fail
+ * `buffer_size`: The default maximum buffer size to use for a test case. Defaults to `100_000`.
+
+!!! warn "Buffer Size"
+    At any one point, there may be more than one active buffer being worked on.
+    You can try to increase this value when you encounter a lot of `Overrun`.
+    Do not set this too large, or you're very likely to run out of memory; the default
+    results in ~800kB worth of choices being possible, which should be plenty for most fuzzing
+    tasks. It's generally unlikely that failures only occur with very large values here, and not with
+    smaller ones.
 """
 struct CheckConfig
     rng::Random.AbstractRNG
@@ -83,8 +92,9 @@ struct CheckConfig
     verbose::Bool
     broken::Bool
     db::ExampleDB
+    buffer_size::UInt
     function CheckConfig(; rng::Random.AbstractRNG, max_examples::Int, record=true,
-                            verbose=false, broken=false, db::Union{Bool,ExampleDB}=true, kws...)
+                            verbose=false, broken=false, db::Union{Bool,ExampleDB}=true, buffer_size=100_000, kws...)
         !isempty(kws) && @warn "Got unsupported keyword arguments to CheckConfig! Ignoring:" Keywords=keys(kws)
         database::ExampleDB = if db isa Bool
             if db
@@ -100,7 +110,8 @@ struct CheckConfig
             record,
             verbose,
             broken,
-            database)
+            database,
+            buffer_size)
     end
 end
 

test/runtests.jl

@@ -811,12 +811,19 @@ const verb = VERSION.major == 1 && VERSION.minor < 11
         end
 
         @testset "Partially overwrite given Config" begin
-            cntr = Ref(0)
-            @check config=conf max_examples=100 function passConfFailTestFailTest(i=intgen)
-                cntr[] += 1
+            res = @check config=conf max_examples=100 function passConfFailTestFailTest(i=intgen)
                 true
             end
-            @test cntr[] == 100
+            @test @something(res.final_state).calls == 100
+        end
+
+        @testset "Buffer Size" begin
+            vecgen = Data.Vectors(Data.Integers{UInt8}(); min_size=10)
+            res = @check buffer_size=1 record=false function passConfFailTestFailTest(v=vecgen)
+                isempty(v)
+            end
+            # all of these must have been rejected as an Overrun, so no call should ever take place
+            @test iszero(@something(res.final_state).valid_test_cases)
         end
     end