Update runtests.jl

test/runtests.jl

@@ -1,11 +1,25 @@
 using CoverageTools
 using Test
 
-if VERSION < v"1.1-"
+if Base.VERSION < v"1.1"
     isnothing(x) = false
     isnothing(x::Nothing) = true
 end
 
+if Base.VERSION < v"1.4"
+    function only(x::Array)
+        i = iterate(x)
+        @boundscheck if i === nothing
+            throw(ArgumentError("Collection is empty, must contain exactly 1 element"))
+        end
+        (ret, state) = i::NTuple{2,Any}
+        @boundscheck if iterate(x, state) !== nothing
+            throw(ArgumentError("Collection has multiple elements, must contain exactly 1 element"))
+        end
+        return ret
+    end
+end
+
 withenv("DISABLE_AMEND_COVERAGE_FROM_SRC" => nothing) do
 
 @testset "iscovfile" begin