diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0034c11..0c6e2a3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,6 +1,12 @@
 name: CI
 env:
   JULIA_NUM_THREADS: 2
+concurrency:
+  # group by workflow and ref; the last slightly strange component ensures that for pull
+  # requests, we limit to 1 concurrent job, but for the master branch we don't
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ (github.ref != 'refs/heads/master' && github.ref != 'refs/heads/main') || github.run_number }}
+  # Cancel intermediate builds, but only if it is a pull request build.
+  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
 on:
   pull_request:
     branches:
diff --git a/Project.toml b/Project.toml
index 50a0965..076ef7e 100644
--- a/Project.toml
+++ b/Project.toml
@@ -26,10 +26,3 @@ JuMP = "1"
 LEMONGraphs = "0.1.0"
 MathOptInterface = "1"
 julia = "1.10"
-
-[extras]
-Cbc = "9961bab8-2fa3-5c5a-9d89-47fab24efd76"
-Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
-
-[targets]
-test = ["Test", "Cbc"]
diff --git a/test/Project.toml b/test/Project.toml
index da4b9f3..9c9878a 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -1,6 +1,6 @@
 [deps]
-Cbc = "9961bab8-2fa3-5c5a-9d89-47fab24efd76"
 Graphs = "86223c79-3864-5bf0-83f7-82e725a168b6"
+HiGHS = "87dc4568-4c63-4d18-b0c0-bb2238e4078b"
 Hungarian = "e91730f6-4275-51fb-a7a0-7064cfbd3b39"
 JuMP = "4076af6c-e467-56ae-b986-b466b2749572"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
diff --git a/test/REQUIRE b/test/REQUIRE
deleted file mode 100644
index b67d6e8..0000000
--- a/test/REQUIRE
+++ /dev/null
@@ -1 +0,0 @@
-Cbc 0.4
diff --git a/test/runtests.jl b/test/runtests.jl
index cd0df89..98a6982 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,7 +1,7 @@
 using Graphs
 using GraphsMatching
 using Test
-using Cbc
+using HiGHS
 using JuMP
 using LinearAlgebra: I
 
@@ -21,7 +21,7 @@ end
             w = transpose(w) * w
             match_sol = maximum_weight_matching(
                 g,
-                optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+                HiGHS.Optimizer,
                 w,
             )
             match_red = maximum_weight_matching_reduction(g, w)
@@ -44,7 +44,7 @@ end
         ]
         match = maximum_weight_matching(
             g,
-            optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            HiGHS.Optimizer,
             w,
         )
         @test match.mate[1] == 3
@@ -57,7 +57,7 @@ end
         w[1, 3] = 1
         match = maximum_weight_matching(
             g,
-            optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            HiGHS.Optimizer,
             w,
         )
         @test match.weight ≈ 1
@@ -75,7 +75,7 @@ end
 
         match = maximum_weight_matching(
             g,
-            optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            HiGHS.Optimizer,
             w,
         )
         @test match.weight ≈ 3
@@ -91,7 +91,7 @@ end
         add_edge!(g, 3, 4)
         match = maximum_weight_matching(
             g,
-            optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            HiGHS.Optimizer,
         )
         @test match.weight ≈ 2
         @test match.mate[1] == 2
@@ -107,7 +107,7 @@ end
 
         match = maximum_weight_matching(
             g,
-            optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            HiGHS.Optimizer,
             w,
         )
         @test match.weight ≈ 2
@@ -124,7 +124,7 @@ end
 
         match = maximum_weight_matching(
             g,
-            optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            HiGHS.Optimizer,
             w,
         )
         @test match.weight ≈ 5
@@ -147,7 +147,7 @@ end
             g,
             w,
             algorithm = LPAlgorithm(),
-            optimizer = optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            optimizer = HiGHS.Optimizer,
         )
         @test match.weight ≈ 21
         @test match.mate[1] == 3
@@ -165,7 +165,7 @@ end
             g,
             w,
             algorithm = LPAlgorithm(),
-            optimizer = optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            optimizer = HiGHS.Optimizer,
         )
         @test match.weight ≈ 11.5
         @test match.mate[1] == 4
@@ -185,7 +185,7 @@ end
             g,
             w,
             algorithm = LPAlgorithm(),
-            optimizer = optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            optimizer = HiGHS.Optimizer,
             cutoff = 0,
         )
         @test match.weight ≈ 11.5
@@ -206,7 +206,7 @@ end
             g,
             w,
             algorithm = LPAlgorithm(),
-            optimizer = optimizer_with_attributes(Cbc.Optimizer, "LogLevel" => 0),
+            optimizer = HiGHS.Optimizer,
             cutoff = 0,
         )
         @test match.weight ≈ 12