Add more set-like version constraint operations.

test/version_test.dart

Index: test/version_test.dart
diff --git a/test/version_test.dart b/test/version_test.dart
index 8745006058e25f387a4c338df2695051134dbae3..e3d1b49a9d6092e73aed4076d556c516c01e8bdb 100644
--- a/test/version_test.dart
+++ b/test/version_test.dart
@@ -138,6 +138,22 @@ main() {
         new Version.parse('1.2.3+build')));
   });
 
+  test('allowsAll()', () {
+    expect(v123.allowsAll(v123), isTrue);
+    expect(v123.allowsAll(v003), isFalse);
+    expect(v123.allowsAll(new VersionRange(min: v114, max: v124)), isFalse);
+    expect(v123.allowsAll(VersionConstraint.any), isFalse);
+    expect(v123.allowsAll(VersionConstraint.empty), isTrue);
+  });
+
+  test('allowsAny()', () {
+    expect(v123.allowsAny(v123), isTrue);
+    expect(v123.allowsAny(v003), isFalse);
+    expect(v123.allowsAny(new VersionRange(min: v114, max: v124)), isTrue);
+    expect(v123.allowsAny(VersionConstraint.any), isTrue);
+    expect(v123.allowsAny(VersionConstraint.empty), isFalse);
+  });
+
   test('intersect()', () {
     // Intersecting the same version returns the version.
     expect(v123.intersect(v123), equals(v123));
@@ -154,6 +170,40 @@ main() {
         isTrue);
   });
 
+  group('union()', () {
+    test("with the same version returns the version", () {
+      expect(v123.union(v123), equals(v123));
+    });
+
+    test("with a different version returns a version that matches both", () {
+      var result = v123.union(v080);
+      expect(result, allows(v123));
+      expect(result, allows(v080));
+
+      // Nothing in between should match.
+      expect(result, doesNotAllow(v114));
+    });
+
+    test("with a range returns the range if it contains the version", () {
+      var range = new VersionRange(min: v114, max: v124);
+      expect(v123.union(range), equals(range));
+    });
+
+    test("with a range with the version on the edge, expands the range", () {
+      expect(v124.union(new VersionRange(min: v114, max: v124)),
+          equals(new VersionRange(min: v114, max: v124, includeMax: true)));
+      expect(v114.union(new VersionRange(min: v114, max: v124)),
+          equals(new VersionRange(min: v114, max: v124, includeMin: true)));
+    });
+
+    test("with a range allows both the range and the version if the range "
+        "doesn't contain the version", () {
+      var result = v123.union(new VersionRange(min: v003, max: v114));
+      expect(result, allows(v123));
+      expect(result, allows(v010));
+    });
+  });
+
   test('isEmpty', () {
     expect(v123.isEmpty, isFalse);
   });