diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index be2aec2..77b8559 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,24 +18,44 @@ jobs:
   # This workflow contains a single job called "build"
   build:
     # The type of runner that the job will run on
-    runs-on: ubuntu-latest
+    runs-on: ${{matrix.os}}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    defaults:
+      run:
+        shell: bash
 
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - uses: actions/checkout@v4
 
-      - name: Install SBCL
-        run: sudo apt-get install sbcl
+      - name: Install SBCL (Linux)
+        if: runner.os == 'Linux'
+        run: sudo apt-get install -y sbcl
+
+      - name: Install SBCL (macOS)
+        if: runner.os == 'macOS'
+        run: brew install sbcl
+
+      - name: Install SBCL (Windows)
+        if: runner.os == 'Windows'
+        run: choco install sbcl
 
       - name: Install Quicklisp and ql-https
-        run: bash install.sh
+        run: ./install.sh
 
       - name: Run tests
+        env:
+          CI: 1
         run: |
           sbcl <<EOF
           (require 'asdf)
+          (push (uiop:getcwd) asdf:*central-registry*)
           (ql:quickload "ql-https/test")
           (asdf:test-system "ql-https")
+          (uiop:quit)
           EOF
-          
+
diff --git a/ql-https.asd b/ql-https.asd
index d282ab7..27750c4 100644
--- a/ql-https.asd
+++ b/ql-https.asd
@@ -25,14 +25,14 @@
 (defsystem "ql-https/test"
   :description "Tests for ql-https"
   :depends-on ((:require "uiop")
-               "fiasco"
+               "fiveam"
                "ql-https")
   :pathname "t/"
   :components ((:file "tests"))
   :perform (test-op (op c)
-                    (unless (uiop:symbol-call :fiasco :run-package-tests :package :ql-https/test)
-                      #+(not (or :swank :slynk))
-                      (error "Tests failed."))))
+                    (unless (uiop:symbol-call :fiveam :run! :ql-https)
+                      (when (uiop:getenvp "CI")
+                        (uiop:quit 1)))))
 
 
 
diff --git a/t/tests.lisp b/t/tests.lisp
index 44640ce..95d91b9 100644
--- a/t/tests.lisp
+++ b/t/tests.lisp
@@ -2,41 +2,45 @@
 ;;; License, v. 2.0. If a copy of the MPL was not distributed with this
 ;;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-(fiasco:define-test-package :ql-https/test)
+(defpackage #:ql-https/test
+  (:use :cl :fiveam))
+
 (in-package #:ql-https/test)
 
-(defmacro wait ((&key (timeout 10)) &body body)
+(def-suite* :ql-https)
+
+(defmacro wait ((&key (timeout 20)) &body body)
   (let ((gthread (gensym "thread")))
     `(let ((,gthread (sb-thread:make-thread (lambda ()
                                               (progn ,@body)))))
        (sb-thread:join-thread ,gthread :timeout ,timeout))))
 
-(deftest test-ql-https-is-initialized-correctly ()
+(test test-ql-https-is-initialized-correctly
   (let ((http-function (cdr (assoc "http" ql-http:*fetch-scheme-functions* :test #'string=)))
         (https-function (cdr (assoc "https" ql-http:*fetch-scheme-functions* :test #'string=))))
     (is (eq 'ql-https:fetcher http-function) "HTTP doesn't use `ql-https:fetch'")
     (is (eq 'ql-https:fetcher https-function) "HTTP doesn't use `ql-https:fetch'")))
 
-(deftest test-downloading-system ()
+(test test-downloading-system
   (ql:uninstall "str")
   (let ((ql-https:*quietly-use-https* nil))
     (signals ql-https:no-https-error
       (ql:quickload "str" :silent t))))
 
-(deftest test-quicklisp-download ()
+(test test-quicklisp-download
   (ql:uninstall "str")
   (wait ()
-    (let ((ql-https:*quietly-use-https* t))
-      (ql:quickload "str" :silent t)))
+        (let ((ql-https:*quietly-use-https* t))
+          (ql:quickload "str" :silent t)))
   (is (find-package :str)))
 
-(deftest test-ultralisp-download ()
+(test test-ultralisp-download
   (ql:uninstall "hyperdoc")
   (wait ()
-    (let ((ql-https:*quietly-use-https* t))
-      ;; install ultralisp
-      (ql-dist:install-dist "https://dist.ultralisp.org/" :prompt nil :replace t)
-      (ql:quickload "hyperdoc" :silent t)))
+        (let ((ql-https:*quietly-use-https* t))
+          ;; install ultralisp
+          (ql-dist:install-dist "https://dist.ultralisp.org/" :prompt nil :replace t)
+          (ql:quickload "hyperdoc" :silent t)))
   (is (find-package :hyperdoc)))