diff --git a/client/__tests__/util/nameCreators.test.js b/client/__tests__/util/nameCreators.test.js
new file mode 100644
index 00000000..5c6f462c
--- /dev/null
+++ b/client/__tests__/util/nameCreators.test.js
@@ -0,0 +1,68 @@
+/*
+Test cases for nameCreators.js.
+*/
+import {
+  layoutDimensionName,
+  obsAnnoDimensionName,
+  diffexpDimensionName,
+  userDefinedDimensionName,
+  makeContinuousDimensionName
+} from "../../src/util/nameCreators";
+
+describe("nameCreators", () => {
+  const nameCreators = [
+    layoutDimensionName,
+    obsAnnoDimensionName,
+    diffexpDimensionName,
+    userDefinedDimensionName
+  ];
+
+  test("check for namespace isolation", () => {
+    const foo = "foo";
+    nameCreators.forEach(fn => expect(fn(foo)).not.toBe(foo));
+
+    const bar = "bar";
+    nameCreators.forEach(fn => expect(fn(foo)).not.toBe(fn(bar)));
+
+    nameCreators.forEach(fn => {
+      const allOtherFn = nameCreators.filter(elmnt => elmnt !== fn);
+      allOtherFn.forEach(otherFn => expect(fn(foo)).not.toBe(otherFn(foo)));
+    });
+  });
+
+  test("check for legal keys", () => {
+    /* need namespace creators to return strings only */
+    nameCreators.forEach(fn => expect(fn("X")).toMatch(/X/));
+  });
+});
+
+describe("makeContinuousDimensionName", () => {
+  test("namespaces", () => {
+    expect(makeContinuousDimensionName({ isObs: true }, "OK")).toMatch(/OK/);
+    expect(makeContinuousDimensionName({ isDiffExp: true }, "OK")).toMatch(
+      /OK/
+    );
+    expect(makeContinuousDimensionName({ isUserDefined: true }, "OK")).toMatch(
+      /OK/
+    );
+  });
+
+  test("error handling", () => {
+    expect(() => makeContinuousDimensionName({}, "oops")).toThrow();
+    expect(() =>
+      makeContinuousDimensionName(
+        { isObs: false, isDiffExp: false, isUserDefined: false },
+        "oops"
+      )
+    ).toThrow();
+    expect(() =>
+      makeContinuousDimensionName({ isObs: true }, "OK")
+    ).not.toThrow();
+    expect(() =>
+      makeContinuousDimensionName({ isDiffExp: true }, "OK")
+    ).not.toThrow();
+    expect(() =>
+      makeContinuousDimensionName({ isUserDefined: true }, "OK")
+    ).not.toThrow();
+  });
+});
diff --git a/client/__tests__/util/stateManager/world.test.js b/client/__tests__/util/stateManager/world.test.js
index b7a6aa4a..4cae7872 100644
--- a/client/__tests__/util/stateManager/world.test.js
+++ b/client/__tests__/util/stateManager/world.test.js
@@ -3,15 +3,40 @@ import * as Universe from "../../../src/util/stateManager/universe";
 import * as World from "../../../src/util/stateManager/world";
 import Crossfilter from "../../../src/util/typedCrossfilter";
 import * as REST from "./sampleResponses";
-import { obsAnnoDimensionName } from "../../../src/util/nameCreators";
+import {
+  obsAnnoDimensionName,
+  layoutDimensionName
+} from "../../../src/util/nameCreators";
+import * as kvCache from "../../../src/util/stateManager/keyvalcache";
 
 /*
-TODO: endpoints to test:
-
-createObsDimensionMap(crossfilter, world)
-subsetVarData(world, universe, varData)
-
+Helper - creates universe, world, corssfilter and dimensionMap from
+the default REST test response.
 */
+const defaultBigBang = () => {
+  /* create unverse, world, crossfilter and dimensionMap */
+  /* create universe */
+  const universe = Universe.createUniverseFromRestV02Response(
+    REST.config,
+    REST.schema,
+    REST.annotationsObs,
+    REST.annotationsVar,
+    REST.layoutObs
+  );
+  /* create world */
+  const world = World.createWorldFromEntireUniverse(universe);
+  /* create crossfilter */
+  const crossfilter = Crossfilter(world.obsAnnotations);
+  /* create dimension map */
+  const dimensionMap = World.createObsDimensionMap(crossfilter, world);
+
+  return {
+    universe,
+    world,
+    crossfilter,
+    dimensionMap
+  };
+};
 
 describe("createWorldFromEntireUniverse", () => {
   test("create from REST sample", () => {
@@ -55,24 +80,14 @@ describe("createWorldFromEntireUniverse", () => {
 
 describe("createWorldFromCurrentSelection", () => {
   test("create from REST sample", () => {
-    /* create universe */
-    const universe = Universe.createUniverseFromRestV02Response(
-      REST.config,
-      REST.schema,
-      REST.annotationsObs,
-      REST.annotationsVar,
-      REST.layoutObs
-    );
-    /* create world */
-    const originalWorld = World.createWorldFromEntireUniverse(universe);
-    /* create crossfilter */
-    const crossfilter = Crossfilter(originalWorld.obsAnnotations);
-
-    /* fake a selection */
-    const dimensionMap = World.createObsDimensionMap(
+    const {
+      universe,
+      world: originalWorld,
       crossfilter,
-      originalWorld
-    );
+      dimensionMap
+    } = defaultBigBang();
+
+    /* mock a selection */
     dimensionMap[obsAnnoDimensionName("field1")].filterRange([0, 5]);
     dimensionMap[obsAnnoDimensionName("field3")].filterExact(false);
 
@@ -128,3 +143,87 @@ describe("createWorldFromCurrentSelection", () => {
     );
   });
 });
+
+describe("createObsDimensionMap", () => {
+  test("when universe eq world", () => {
+    /*
+    check for:
+    - creates a dimension for all obsAnnotations, PLUS X/Y layout
+    - check that dimension typing is sane
+    */
+
+    const { dimensionMap } = defaultBigBang();
+
+    const schemaByObsName = _.keyBy(REST.schema.schema.annotations.obs, "name");
+    expect(dimensionMap).toBeDefined();
+    REST.annotationsObs.names.forEach(name => {
+      const dim = dimensionMap[obsAnnoDimensionName(name)];
+      const { type } = schemaByObsName[name];
+      if (type === "string" || type === "boolean" || type === "categorical") {
+        expect(dim).toBeInstanceOf(Crossfilter.EnumDimension);
+      } else {
+        expect(dim).toBeInstanceOf(Crossfilter.ScalarDimension);
+      }
+    });
+    expect(dimensionMap[layoutDimensionName("X")]).toBeInstanceOf(
+      Crossfilter.ScalarDimension
+    );
+    expect(dimensionMap[layoutDimensionName("Y")]).toBeInstanceOf(
+      Crossfilter.ScalarDimension
+    );
+  });
+});
+
+describe("subsetVarData", () => {
+  test("when world eq universe", () => {
+    const { universe, world } = defaultBigBang();
+    /* create a mock varData array for subsetting */
+    const sourceVarData = new Float32Array(universe.nObs);
+
+    /* expect literally the same object back */
+    const result = World.subsetVarData(world, universe, sourceVarData);
+    expect(result).toBe(sourceVarData);
+  });
+
+  test("when world neq universe", () => {
+    const { universe, world, crossfilter, dimensionMap } = defaultBigBang();
+    /* create a mock varData array for subsetting */
+    const sourceVarData = Float32Array.from(_.range(universe.nObs));
+
+    /* mock a selection */
+    dimensionMap[obsAnnoDimensionName("field1")].filterRange([0, 5]);
+    dimensionMap[obsAnnoDimensionName("field3")].filterExact(false);
+
+    /* create the world from the selection */
+    const newWorld = World.createWorldFromCurrentSelection(
+      universe,
+      world,
+      crossfilter
+    );
+
+    /* expect a subset */
+    const result = World.subsetVarData(newWorld, universe, sourceVarData);
+    expect(result).not.toBe(sourceVarData);
+    expect(result).toHaveLength(newWorld.nObs);
+    /* check that we have expected source var content */
+    expect(result).toMatchObject(new Float32Array([0, 2]));
+  });
+});
+
+describe("createVarDimension", () => {
+  /* create default universe */
+  const { world, crossfilter } = defaultBigBang();
+  /* create a mock var data cache */
+  const varDataCache = kvCache.set(
+    kvCache.create(),
+    "GENE",
+    Float32Array.from(_.range(world.nObs))
+  );
+  const result = World.createVarDimension(
+    world,
+    varDataCache,
+    crossfilter,
+    "GENE"
+  );
+  expect(result).toBeInstanceOf(Crossfilter.ScalarDimension);
+});
diff --git a/client/src/util/nameCreators.js b/client/src/util/nameCreators.js
index e7ec1612..a4237c58 100644
--- a/client/src/util/nameCreators.js
+++ b/client/src/util/nameCreators.js
@@ -37,6 +37,8 @@ export const makeContinuousDimensionName = (continuousNamespace, key) => {
     name = diffexpDimensionName(key);
   } else if (continuousNamespace.isUserDefined) {
     name = userDefinedDimensionName(key);
+  } else {
+    throw new Error("unknown continuous dimension");
   }
 
   return name;