--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/layout/suffixLabels.test.ts	Sun Mar 13 22:00:30 2022 -0700
@@ -0,0 +1,70 @@
+import { SuffixLabels } from './suffixLabels';
+
+describe('_tailSegments', () => {
+  it("returns right amount", () => {
+    expect(SuffixLabels._tailSegments('http://foo/a/bb', 0)).toEqual('');
+    expect(SuffixLabels._tailSegments('http://foo/a/bb', 1)).toEqual('bb');
+    expect(SuffixLabels._tailSegments('http://foo/a/bb', 2)).toEqual('a/bb');
+    expect(SuffixLabels._tailSegments('http://foo/a/bb', 3)).toEqual('foo/a/bb');
+    expect(SuffixLabels._tailSegments('http://foo/a/bb', 4)).toEqual('/foo/a/bb');
+    expect(SuffixLabels._tailSegments('http://foo/a/bb', 5)).toEqual('http://foo/a/bb');
+  });
+  it("_tailSegments ok with trailing slash", () => {
+    expect(SuffixLabels._tailSegments('http://foo/', 0)).toEqual('');
+    expect(SuffixLabels._tailSegments('http://foo/', 1)).toEqual('');
+    expect(SuffixLabels._tailSegments('http://foo/', 2)).toEqual('foo/');
+  });
+});
+
+describe("suffixLabels", () => {
+  const fakeNode = (uri: string) => { return { nominalValue: uri } };
+
+  it("returns whole url segments", () => {
+    const suf = new SuffixLabels();
+    suf._planDisplayForUri('http://a/b/c/dd');
+    suf._planDisplayForUri('http://a/b/c/ee');
+
+    expect(suf.getLabelForNode('http://a/b/c/dd')).toEqual('dd');
+    expect(suf.getLabelForNode('http://a/b/c/ee')).toEqual('ee');
+  });
+
+  it("doesn't treat a repeated uri as a name clash", () => {
+    const suf = new SuffixLabels();
+    suf._planDisplayForUri('http://a/b/c');
+    suf._planDisplayForUri('http://a/b/c');
+
+    expect(suf.getLabelForNode('http://a/b/c')).toEqual('c');
+  });
+
+  it("moves to two segments when needed", () => {
+    const suf = new SuffixLabels();
+    suf._planDisplayForUri('http://a/b/c/d');
+    suf._planDisplayForUri('http://a/b/f/d');
+
+    expect(suf.getLabelForNode('http://a/b/c/d')).toEqual('c/d');
+    expect(suf.getLabelForNode('http://a/b/f/d')).toEqual('f/d');
+  });
+
+  it("is ok with clashes at different segment positions", () => {
+    const suf = new SuffixLabels();
+    suf._planDisplayForUri('http://z/z/z/a/b/c');
+    suf._planDisplayForUri('http://a/b/c');
+
+    expect(suf.getLabelForNode('http://z/z/z/a/b/c')).toEqual('z/a/b/c');
+    expect(suf.getLabelForNode('http://a/b/c')).toEqual('/a/b/c');
+  });
+
+  it("uses appropriately long suffixes per uri", () => {
+    const suf = new SuffixLabels();
+    suf._planDisplayForUri('http://a/b/c/d/e');
+    suf._planDisplayForUri('http://a/b/f/d/e');
+    suf._planDisplayForUri('http://a/b/c/g');
+    suf._planDisplayForUri('http://a/z');
+
+    expect(suf.getLabelForNode('http://a/b/c/d/e')).toEqual('c/d/e');
+    expect(suf.getLabelForNode('http://a/b/f/d/e')).toEqual('f/d/e');
+    expect(suf.getLabelForNode('http://a/b/c/g')).toEqual('g');
+    expect(suf.getLabelForNode('http://a/z')).toEqual('z');
+  });
+
+});
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