diff --git a/test/common.jl b/test/common.jl
index 3a04608..2f52ec0 100644
--- a/test/common.jl
+++ b/test/common.jl
@@ -375,6 +375,18 @@ function test_clamp_nan(TX::Type)
     end
 end
 
+function test_sign_related(TX::Type)
+    for X in target(TX, :i8; ex = :thin)
+        # `FixedPoint` is not a signed or unsigned integer type
+        @test_throws Exception signed(X)
+        @test_throws Exception signed(X(0.5))
+        @test_throws Exception unsigned(X)
+        @test_throws Exception unsigned(X(0.5))
+
+        @test signbit(X(0.5)) === signbit(X(0.0)) === false
+    end
+end
+
 function test_isinteger(TX::Type)
     @testset "isinteger(::$X)" for X in target(TX, :i8, :i16)
         xs = typemin(X):eps(X):typemax(X)
diff --git a/test/fixed.jl b/test/fixed.jl
index bcfce6d..baa4c3a 100644
--- a/test/fixed.jl
+++ b/test/fixed.jl
@@ -614,19 +614,17 @@ end
 end
 
 @testset "sign-related functions" begin
-    @test_throws Exception signed(Q0f7)
-    @test_throws Exception signed(0.5Q0f7)
-    @test_throws Exception unsigned(Q0f7)
-    @test_throws Exception unsigned(0.5Q0f7)
+    test_sign_related(Fixed)
+
     @test copysign(0.5Q0f7, 0x1) === 0.5Q0f7
     @test copysign(0.5Q0f7, -1) === -0.5Q0f7
     @test flipsign(0.5Q0f7, 0x1) === 0.5Q0f7
     @test flipsign(0.5Q0f7, -1) === -0.5Q0f7
-    @test_throws ArgumentError sign(0Q0f7)
+    @test_broken sign(0Q0f7) === zero(Q0f7)
+    @test_throws ArgumentError sign(0.5Q0f7)
     @test sign(0Q1f6) === 0Q1f6
     @test sign(0.5Q1f6) === 1Q1f6
     @test sign(-0.5Q1f6) === -1Q1f6
-    @test signbit(0.5Q0f7) === false
     @test signbit(-0.5Q0f7) === true
 end
 
diff --git a/test/normed.jl b/test/normed.jl
index 03f73fa..8c1010a 100644
--- a/test/normed.jl
+++ b/test/normed.jl
@@ -596,16 +596,14 @@ end
 end
 
 @testset "sign-related functions" begin
-    @test_throws Exception signed(N0f8)
-    @test_throws Exception signed(1N0f8)
-    @test_throws Exception unsigned(N0f8)
-    @test_throws Exception unsigned(1N0f8)
+    test_sign_related(Normed)
+
     @test_throws ArgumentError copysign(1N0f8, 0x1)
     @test_throws ArgumentError copysign(1N0f8, -1)
     @test_throws ArgumentError flipsign(1N0f8, 0x1)
     @test_throws ArgumentError flipsign(1N0f8, -1)
-    @test_throws ArgumentError sign(0N0f8)
-    @test signbit(1N0f8) === false
+    @test_broken sign(0N0f8) === zero(N0f8)
+    @test_broken sign(0.5N0f8) === oneunit(N0f8)
 end
 
 @testset "bitwise" begin