diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 63019aa44..304e8dc95 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -47,7 +47,7 @@ jobs:
           - version: '1'
             os: ubuntu-latest
             arch: x86
-            num_threads: 2
+            num_threads: 1
           # Windows
           - version: '1'
             os: windows-latest
diff --git a/test/debug_utils.jl b/test/debug_utils.jl
index dfa46affc..3fc877503 100644
--- a/test/debug_utils.jl
+++ b/test/debug_utils.jl
@@ -199,7 +199,14 @@
             @test retype <: Tuple
 
             # Just make sure the following is runnable.
-            @test (DynamicPPL.DebugUtils.model_warntype(model); true)
+            # Suppress output to avoid GHA slowdown(?)
+            @test begin
+                oldstd = stdout
+                redirect_stdout(devnull)
+                DynamicPPL.DebugUtils.model_warntype(model)
+                redirect_stdout(oldstd)
+                true
+            end
         end
     end
 end
diff --git a/test/lkj.jl b/test/lkj.jl
index b9c20f916..d581cd21b 100644
--- a/test/lkj.jl
+++ b/test/lkj.jl
@@ -22,14 +22,14 @@ _lkj_atol = 0.05
     model = lkj_prior_demo()
     # `SampleFromPrior` will sample in constrained space.
     @testset "SampleFromPrior" begin
-        samples = sample(model, SampleFromPrior(), 1_000)
+        samples = sample(model, SampleFromPrior(), 1_000; progress=false)
         @test mean(map(Base.Fix2(getindex, Colon()), samples)) ≈ target_mean atol =
             _lkj_atol
     end
 
     # `SampleFromUniform` will sample in unconstrained space.
     @testset "SampleFromUniform" begin
-        samples = sample(model, SampleFromUniform(), 1_000)
+        samples = sample(model, SampleFromUniform(), 1_000; progress=false)
         @test mean(map(Base.Fix2(getindex, Colon()), samples)) ≈ target_mean atol =
             _lkj_atol
     end
@@ -39,7 +39,7 @@ end
     model = lkj_chol_prior_demo(uplo)
     # `SampleFromPrior` will sample in unconstrained space.
     @testset "SampleFromPrior" begin
-        samples = sample(model, SampleFromPrior(), 1_000)
+        samples = sample(model, SampleFromPrior(), 1_000; progress=false)
         # Build correlation matrix from factor
         corr_matrices = map(samples) do s
             M = reshape(s.metadata.vals, (2, 2))
@@ -50,7 +50,7 @@ end
 
     # `SampleFromUniform` will sample in unconstrained space.
     @testset "SampleFromUniform" begin
-        samples = sample(model, SampleFromUniform(), 1_000)
+        samples = sample(model, SampleFromUniform(), 1_000; progress=false)
         # Build correlation matrix from factor
         corr_matrices = map(samples) do s
             M = reshape(s.metadata.vals, (2, 2))
diff --git a/test/runtests.jl b/test/runtests.jl
index aea02a337..a8d0e4603 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -42,7 +42,7 @@ Random.seed!(100)
 
 include("test_util.jl")
 
-@testset "DynamicPPL.jl" begin
+@testset verbose=true "DynamicPPL.jl" begin
     if GROUP == "All" || GROUP == "DynamicPPL"
         @testset "interface" begin
             include("utils.jl")
@@ -114,6 +114,7 @@ include("test_util.jl")
                 # This is a line that starts with "└ @ " and ends with the line number.
                 r"└ @ .+:[0-9]+",
             ]
+            GC.gc()
             doctest(DynamicPPL; manual=false, doctestfilters=doctestfilters)
         end
     end