diff --git a/src/module/selector/blend.ts b/src/module/selector/blend.ts
index 26b4178..d424738 100644
--- a/src/module/selector/blend.ts
+++ b/src/module/selector/blend.ts
@@ -11,7 +11,7 @@ class Blend {
   }
 
   public getValue(x: number, y: number, z: number) {
-    if (!(this.sourceModules.length < 2)) {
+    if (this.sourceModules.length < 2) {
       throw new Error('Invalid or missing source module(s)!');
     }
 
diff --git a/src/module/selector/select.ts b/src/module/selector/select.ts
index cd7e7b9..a5e7167 100644
--- a/src/module/selector/select.ts
+++ b/src/module/selector/select.ts
@@ -58,7 +58,7 @@ class Select {
   }
 
   public getValue(x: number, y: number, z: number) {
-    if (!(this.sourceModules.length < 2)) {
+    if (this.sourceModules.length < 2) {
       throw new Error('Invalid or missing source module(s)!');
     }
 
diff --git a/test/module/selector/blend.test.ts b/test/module/selector/blend.test.ts
new file mode 100644
index 0000000..9cd461d
--- /dev/null
+++ b/test/module/selector/blend.test.ts
@@ -0,0 +1,108 @@
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+
+import { Const } from '@app/module/generator';
+import { Blend } from '@app/module/selector';
+
+describe('module/selector/blend', () => {
+  it("can construct successfully", () => {
+    // Setup
+    const sourceValueA = 2;
+    const sourceModuleA = new Const(sourceValueA);
+    const sourceValueB = 2;
+    const sourceModuleB = new Const(sourceValueB);
+    const controlValue = 0.5;
+    const controlModule = new Const(controlValue);
+
+    // Test
+    const testFunc = () => {
+      new Blend([sourceModuleA, sourceModuleB], controlModule);
+    };
+
+    // Assert
+    expect(testFunc).not.to.throw();
+  });
+
+  it("calling getValue with 0 sourceModules throws an error", () => {
+    // Setup
+    const x = 10;
+    const y = 10;
+    const z = 10;
+    const controlValue = 0.5;
+    const controlModule = new Const(controlValue);
+    const mockModule = new Blend([], controlModule);
+
+    // Test
+    const testFunc = () => {
+      mockModule.getValue(x, y, z);
+    };
+
+    // Assert
+    expect(testFunc).to.throw();
+  });
+
+  it("calling getValue with 1 sourceModule throws an error", () => {
+    // Setup
+    const x = 10;
+    const y = 10;
+    const z = 10;
+    const sourceValueA = 2;
+    const sourceModuleA = new Const(sourceValueA);
+    const controlValue = 0.5;
+    const controlModule = new Const(controlValue);
+    const mockModule = new Blend([sourceModuleA], controlModule);
+
+    // Test
+    const testFunc = () => {
+      mockModule.getValue(x, y, z);
+    };
+
+    // Assert
+    expect(testFunc).to.throw();
+  });
+
+  it("calling getValue with no controlModule throws an error", () => {
+    // Setup
+    const x = 10;
+    const y = 10;
+    const z = 10;
+    const sourceValueA = 2;
+    const sourceModuleA = new Const(sourceValueA);
+    const sourceValueB = 2;
+    const sourceModuleB = new Const(sourceValueB);
+    const mockModule = new Blend([sourceModuleA, sourceModuleB]);
+
+    // Test
+    const testFunc = () => {
+      mockModule.getValue(x, y, z);
+    };
+
+    // Assert
+    expect(testFunc).to.throw();
+  });
+
+  it("calling getValue returns a number", () => {
+    // Setup
+    const x = 10;
+    const y = 10;
+    const z = 10;
+    const mockModule = createMockModule();
+
+    // Test
+    const value = mockModule.getValue(x, y, z);
+
+    // Assert
+    expect(value).to.be.ok;
+  });
+});
+
+function createMockModule() {
+  const sourceValueA = 2;
+  const sourceModuleA = new Const(sourceValueA);
+  const sourceValueB = 2;
+  const sourceModuleB = new Const(sourceValueB);
+  const controlValue = 0.5;
+  const controlModule = new Const(controlValue);
+
+  return new Blend([sourceModuleA, sourceModuleB], controlModule);
+}
diff --git a/test/module/selector/select.test.ts b/test/module/selector/select.test.ts
new file mode 100644
index 0000000..6344a8d
--- /dev/null
+++ b/test/module/selector/select.test.ts
@@ -0,0 +1,194 @@
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+
+import { Const } from '@app/module/generator';
+import { Select } from '@app/module/selector';
+
+describe('module/selector/select', () => {
+  it("can construct successfully", () => {
+    // Setup
+    const sourceValueA = 2;
+    const sourceModuleA = new Const(sourceValueA);
+    const sourceValueB = 2;
+    const sourceModuleB = new Const(sourceValueB);
+    const controlValue = 0.5;
+    const controlModule = new Const(controlValue);
+    const edgeFalloff = 1;
+    const lowerBound = -0.5;
+    const upperBound = 0.5;
+
+    // Test
+    const testFunc = () => {
+      new Select([sourceModuleA, sourceModuleB], controlModule, edgeFalloff, lowerBound, upperBound);
+    };
+
+    // Assert
+    expect(testFunc).not.to.throw();
+  });
+
+  it("calling getValue with 0 sourceModules throws an error", () => {
+    // Setup
+    const x = 10;
+    const y = 10;
+    const z = 10;
+    const controlValue = 0.5;
+    const controlModule = new Const(controlValue);
+    const edgeFalloff = 1;
+    const lowerBound = -0.5;
+    const upperBound = 0.5;
+
+    const mockModule = new Select([], controlModule, edgeFalloff, lowerBound, upperBound);
+
+    // Test
+    const testFunc = () => {
+      mockModule.getValue(x, y, z);
+    };
+
+    // Assert
+    expect(testFunc).to.throw();
+  });
+
+  it("calling getValue with 1 sourceModule throws an error", () => {
+    // Setup
+    const x = 10;
+    const y = 10;
+    const z = 10;
+    const sourceValueA = 2;
+    const sourceModuleA = new Const(sourceValueA);
+    const controlValue = 0.5;
+    const controlModule = new Const(controlValue);
+    const edgeFalloff = 1;
+    const lowerBound = -0.5;
+    const upperBound = 0.5;
+
+    const mockModule = new Select([sourceModuleA], controlModule, edgeFalloff, lowerBound, upperBound);
+
+    // Test
+    const testFunc = () => {
+      mockModule.getValue(x, y, z);
+    };
+
+    // Assert
+    expect(testFunc).to.throw();
+  });
+
+  it("calling getValue with no controlModule throws an error", () => {
+    // Setup
+    const x = 10;
+    const y = 10;
+    const z = 10;
+    const sourceValueA = 2;
+    const sourceModuleA = new Const(sourceValueA);
+    const sourceValueB = 2;
+    const sourceModuleB = new Const(sourceValueB);
+    const edgeFalloff = 1;
+    const lowerBound = -0.5;
+    const upperBound = 0.5;
+
+    const mockModule = new Select([sourceModuleA, sourceModuleB], null, edgeFalloff, lowerBound, upperBound);
+
+    // Test
+    const testFunc = () => {
+      mockModule.getValue(x, y, z);
+    };
+
+    // Assert
+    expect(testFunc).to.throw();
+  });
+
+  it("calling getValue returns a number", () => {
+    // Setup
+    const x = 10;
+    const y = 10;
+    const z = 10;
+    const mockModule = createMockModule();
+
+    // Test
+    const value = mockModule.getValue(x, y, z);
+
+    // Assert
+    expect(value).to.be.ok;
+  });
+
+  it("setting edge updates correctly", () => {
+    // Setup
+    const newEdgeValue = 0.2;
+    const mockModule = createMockModule();
+
+    // Test
+    mockModule.edge = newEdgeValue;
+    const updatedEdgeValue = mockModule.edge;
+
+    // Assert
+    expect(updatedEdgeValue).to.equal(newEdgeValue);
+  });
+
+  it("setting lowerBound updates correctly", () => {
+    // Setup
+    const newLowerBoundValue = -1;
+    const mockModule = createMockModule();
+
+    // Test
+    mockModule.lowerBound = newLowerBoundValue;
+    const updatedLowerBoundValue = mockModule.lowerBound;
+
+    // Assert
+    expect(updatedLowerBoundValue).to.equal(newLowerBoundValue);
+  });
+
+  it("setting lowerBound to a value higher than upperBound throws an error", () => {
+    // Setup
+    const mockModule = createMockModule();
+    const newLowerBoundValue = mockModule.upperBound + 1;
+
+    // Test
+    const testFunc = () => {
+      mockModule.lowerBound = newLowerBoundValue;
+    };
+
+    // Assert
+    expect(testFunc).to.throw();
+  });
+
+  it("setting upperBound updates correctly", () => {
+    // Setup
+    const newUpperBoundValue = 2;
+    const mockModule = createMockModule();
+
+    // Test
+    mockModule.upperBound = newUpperBoundValue;
+    const updatedUpperBoundValue = mockModule.upperBound;
+
+    // Assert
+    expect(updatedUpperBoundValue).to.equal(newUpperBoundValue);
+  });
+
+  it("setting upperBound to a value higher than lowerBound throws an error", () => {
+    // Setup
+    const mockModule = createMockModule();
+    const newUpperBoundValue = mockModule.lowerBound - 1;
+
+    // Test
+    const testFunc = () => {
+      mockModule.upperBound = newUpperBoundValue;
+    };
+
+    // Assert
+    expect(testFunc).to.throw();
+  });
+});
+
+function createMockModule() {
+  const sourceValueA = 2;
+  const sourceModuleA = new Const(sourceValueA);
+  const sourceValueB = 2;
+  const sourceModuleB = new Const(sourceValueB);
+  const controlValue = 0.5;
+  const controlModule = new Const(controlValue);
+  const edgeFalloff = 1;
+  const lowerBound = -0.5;
+  const upperBound = 0.5;
+
+  // Test
+  return new Select([sourceModuleA, sourceModuleB], controlModule, edgeFalloff, lowerBound, upperBound);
+}