tests: Fix tests for older Julia

Also a couple of clarity fixes

Author: christiangnrd

src/mutualinfo.jl

@@ -55,17 +55,17 @@ in the denominator is computed. It can be one of:
 """
 function mutualinfo(a, b; method::Union{Nothing, Symbol} = nothing, normed::Union{Nothing, Bool} = nothing, kwargs...)
     # Disallow `method` and `normed` to be used together
-    if isnothing(method)
-        isnothing(normed) || Base.depwarn("`normed` kwarg is deprecated, please use `method=:normalized` instead of `normed=true`, and `method=:classic` instead of `normed=false'", :mutualinfo)
-        method = if isnothing(normed) || normed
+    if method === nothing
+        (normed === nothing) || Base.depwarn("`normed` kwarg is deprecated, please use `method=:normalized` instead of `normed=true`, and `method=:classic` instead of `normed=false'", :mutualinfo)
+        method = if (normed === nothing) || normed
             :normalized
         else
             :classic
         end
     else
-        isnothing(normed) || throw(ArgumentError("`normed` kwarg is not compatible with `method` kwarg"))
+        (normed === nothing) || throw(ArgumentError("`normed` kwarg is not compatible with `method` kwarg"))
     end
-    # Little hack to ensure the correct error is thrown
+    # Little hack to ensure the invalid kwargs error is thrown
     if method === :adjusted && length(kwargs) >= 1 && :aggregate ∉ keys(kwargs)
         method = :classic
     end

test/mutualinfo.jl

@@ -27,10 +27,17 @@ using Clustering
     @test mutualinfo(a1, a2; method=:adjusted, aggregate=:max) ≈ 0.3437 atol=1.0e-4
     @test mutualinfo(a1, a2; method=:adjusted, aggregate=:min) ≈ 0.4348 atol=1.0e-4
 
-    # test errors
-    @test_throws "ArgumentError: `normed` kwarg is not compatible with `method` kwarg" mutualinfo(a1, a2; method=:adjusfted, normed=false)
-    @test_throws "ArgumentError: mutualinfo(): `method=:adjusfted` is not supported" mutualinfo(a1, a2; method=:adjusfted, aggregate=:min)
-    @test_throws "ArgumentError: mutualinfo(): unsupported kwargs used." mutualinfo(a1, a2; method=:adjusted, notaggregate=:min)
-    @test_throws "ArgumentError: mutualinfo(): unsupported kwargs used." mutualinfo(a1, a2; method=:classic, notaggregate=:min)
+    # test errors. More precise tests on Julia 1.8+ when supported
 
+    if VERSION >= v"1.8"
+        @test_throws "ArgumentError: `normed` kwarg is not compatible with `method` kwarg" mutualinfo(a1, a2; method=:adjusted, normed=false)
+        @test_throws "ArgumentError: mutualinfo(): `method=:adjusfted` is not supported" mutualinfo(a1, a2; method=:adjusfted, aggregate=:min)
+        @test_throws "ArgumentError: mutualinfo(): unsupported kwargs used." mutualinfo(a1, a2; method=:adjusted, notaggregate=:min)
+        @test_throws "ArgumentError: mutualinfo(): unsupported kwargs used." mutualinfo(a1, a2; method=:classic, notaggregate=:min)
+    else
+        @test_throws ArgumentError mutualinfo(a1, a2; method=:adjusted, normed=false)
+        @test_throws ArgumentError mutualinfo(a1, a2; method=:adjusfted, aggregate=:min)
+        @test_throws ArgumentError mutualinfo(a1, a2; method=:adjusted, notaggregate=:min)
+        @test_throws ArgumentError mutualinfo(a1, a2; method=:classic, notaggregate=:min)
+    end
 end