diff --git a/test/runtests.jl b/test/runtests.jl
index b77719d..5fd30c2 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -3,7 +3,11 @@ using WignerSymbols
 using LinearAlgebra
 using Random
 using Base.Threads
-N = Base.Threads.nthreads()
+if Base.Sys.iswindows() # not sure why the multithreaded version fails on Windows
+    N = 1
+else
+    N = Base.Threads.nthreads()
+end
 Random.seed!(1234)
 
 smalljlist = 0:1//2:10
@@ -51,9 +55,9 @@ end
 end
 
 # test recurrence relations: Phys Rev E 57, 7274 (1998)
-if Base.Sys.iswindows() # not sure why the multithreaded version fails on Windows
-    @testset "wigner3j: recurrence relations" begin
-        for k = 1:8
+@threads for i = 1:N
+    @testset "wigner3j: recurrence relations, thread $i" begin
+        for k = 1:div(8,N)
             j2 = convert(BigFloat, rand(largejlist))
             j3 = convert(BigFloat, rand(largejlist))
             m2 = -convert(BigFloat, rand(-j2:0))
@@ -70,27 +74,6 @@ if Base.Sys.iswindows() # not sure why the multithreaded version fails on Window
             end
         end
     end
-else
-    @threads for i = 1:N
-        @testset "wigner3j: recurrence relations, thread $i" begin
-            for k = 1:div(8,N)
-                j2 = convert(BigFloat, rand(largejlist))
-                j3 = convert(BigFloat, rand(largejlist))
-                m2 = -convert(BigFloat, rand(-j2:0))
-                m3 = convert(BigFloat, rand(-j3:0))
-
-                for j in max(abs(j2-j3),abs(m2+m3))+1:(j2+j3)-1
-                    X = j*sqrt(((j+1)^2-(j2-j3)^2)*((j2+j3+1)^2-(j+1)^2)*((j+1)^2-(m2+m3)^2))
-                    Y = (2*j+1)*((m2+m3)*(j2*(j2+1)-j3*(j3+1)) - (m2-m3)*j*(j+1))
-                    Z = (j+1)*sqrt((j^2-(j2-j3)^2)*((j2+j3+1)^2-j^2)*(j^2-(m2+m3)^2))
-                    tol = 10*max(abs(X),abs(Y),abs(Z))*eps(BigFloat)
-                    @test (X*wigner3j(BigFloat,j+1,j2,j3,-m2-m3,m2,m3) +
-                                Z*wigner3j(BigFloat,j-1,j2,j3,-m2-m3,m2,m3)) ≈
-                                    (-Y*wigner3j(BigFloat,j,j2,j3,-m2-m3,m2,m3)) atol=tol
-                end
-            end
-        end
-    end
 end
 
 @threads for i = 1:N