diff --git a/test/preparation.jl b/test/preparation.jl
index b55122c..e77f41c 100644
--- a/test/preparation.jl
+++ b/test/preparation.jl
@@ -65,7 +65,8 @@ end
     @test_throws AssertionError get_embeddings(BitPackedBatchEmbedder(), String[])
 
     # corresponds to OpenAI API v1
-    response1 = Dict(:data => [Dict(:embedding => ones(128, 2))],
+    response1 = Dict(:data => [Dict(:embedding => ones(Float32, 128)),
+            Dict(:embedding => ones(Float32, 128))],
         :usage => Dict(:total_tokens => 2, :prompt_tokens => 2, :completion_tokens => 0))
     schema = TestEchoOpenAISchema(; response = response1, status = 200)
     PT.register_model!(; name = "mock-emb", schema)
diff --git a/test/runtests.jl b/test/runtests.jl
index 7917cdb..ade0051 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -9,6 +9,13 @@ using Aqua
 const PT = PromptingTools
 const RT = RAGTools
 
+# Set a dummy API key for tests using CustomOpenAISchema with mock HTTP servers
+# Required since OpenAI.jl now throws an error when api_key is empty
+# We set the PT global directly since it's loaded at module load time from preferences/ENV
+if isempty(PT.OPENAI_API_KEY)
+    PT.OPENAI_API_KEY = "test-api-key-for-mock-server"
+end
+
 @testset "RAGTools.jl" begin
     @testset "Code quality (Aqua.jl)" begin
         Aqua.test_all(RAGTools)