Ensure SVN is installed before running tests

Author: FractalBoy

.github/workflows/main.yml

@@ -21,6 +21,22 @@ jobs:
         version: ['stable', 'insiders']
 
     steps:
+      - name: Install SVN
+        if: startswith(matrix.os, 'ubuntu')
+        run: |
+          sudo apt-get update
+          sudo apt-get install subversion
+
+      - name: Install SVN
+        if: startswith(matrix.os, 'macOS')
+        run: |
+          brew update
+          brew install subversion
+
+      - name: Install SVN
+        if: startswith(matrix.os, 'windows')
+        run: choco install tortoisesvn
+
       - name: Clone repository
         uses: actions/checkout@v1