diff --git a/Project.toml b/Project.toml
index 30ff4d5..007646b 100644
--- a/Project.toml
+++ b/Project.toml
@@ -17,7 +17,7 @@ Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 [compat]
 Dates = "1"
 IOCapture = "0.2.5"
-Malt = "1.2.1"
+Malt = "1.3.0"
 Printf = "1"
 Random = "1"
 Scratch = "1.3.0"
diff --git a/src/ParallelTestRunner.jl b/src/ParallelTestRunner.jl
index 9d5e078..ae91180 100644
--- a/src/ParallelTestRunner.jl
+++ b/src/ParallelTestRunner.jl
@@ -414,15 +414,36 @@ worker_id(wrkr) = WORKER_IDS[wrkr.proc_pid]
 Add `X` worker processes.
 """
 addworkers(X; kwargs...) = [addworker(; kwargs...) for _ in 1:X]
-function addworker(; env=Vector{Pair{String, String}}())
+
+"""
+    addworker(; env=Vector{Pair{String, String}}(), exename=nothing, exeflags=nothing)
+
+Add a single worker process. 
+
+## Arguments
+- `env`: Vector of environment variable pairs to set for the worker process.
+- `exename`: Custom executable to use for the worker process.
+- `exeflags`: Custom flags to pass to the worker process.
+"""
+function addworker(;
+        env = Vector{Pair{String, String}}(),
+        exename = nothing, exeflags = nothing
+    )
     exe = test_exe()
-    exeflags = exe[2:end]
+    if exename === nothing
+        exename = exe[1]
+    end
+    if exeflags !== nothing
+        exeflags = vcat(exe[2:end], exeflags)
+    else
+        exeflags = exe[2:end]
+    end
 
     push!(env, "JULIA_NUM_THREADS" => "1")
     # Malt already sets OPENBLAS_NUM_THREADS to 1
     push!(env, "OPENBLAS_NUM_THREADS" => "1")
 
-    wrkr = Malt.Worker(;exeflags, env)
+    wrkr = Malt.Worker(; exename, exeflags, env)
     WORKER_IDS[wrkr.proc_pid] = length(WORKER_IDS) + 1
     return wrkr
 end
diff --git a/test/runtests.jl b/test/runtests.jl
index 5971bfe..6c83431 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -68,6 +68,8 @@ end
     function test_worker(name)
         if name == "needs env var"
             return addworker(env = ["SPECIAL_ENV_VAR" => "42"])
+        elseif name == "threads/2"
+            return addworker(exeflags = ["--threads=2"])
         end
         return nothing
     end
@@ -77,6 +79,12 @@ end
         end,
         "doesn't need env var" => quote
             @test !haskey(ENV, "SPECIAL_ENV_VAR")
+        end,
+        "threads/1" => quote
+            @test Base.Threads.nthreads() == 1
+        end,
+        "threads/2" => quote
+            @test Base.Threads.nthreads() == 2
         end
     )
 
@@ -86,6 +94,8 @@ end
     str = String(take!(io))
     @test contains(str, r"needs env var .+ started at")
     @test contains(str, r"doesn't need env var .+ started at")
+    @test contains(str, r"threads/1 .+ started at")
+    @test contains(str, r"threads/2 .+ started at")
     @test contains(str, "SUCCESS")
 end