diff --git a/package.json b/package.json
index a1737ce..0c7e97c 100644
--- a/package.json
+++ b/package.json
@@ -10,7 +10,7 @@
     "export": "node analytics_export/startExport.js",
     "lint": "eslint analytics_export/",
     "lint-fix": "eslint --fix analytics_export/",
-    "pretty": "prettier --write analytics_export",
+    "pretty": "prettier --write analytics_export/ test/",
     "test": "mocha"
   },
   "dependencies": {
@@ -28,6 +28,8 @@
     "eslint-config-prettier": "^6.11.0",
     "eslint-plugin-import": "^2.21.2",
     "mocha": "^8.0.1",
-    "prettier": "^2.0.5"
+    "prettier": "^2.0.5",
+    "proxyquire": "^2.1.3",
+    "sinon": "^9.0.2"
   }
 }
diff --git a/test/testBigqueryClient.js b/test/testBigqueryClient.js
new file mode 100644
index 0000000..51207fc
--- /dev/null
+++ b/test/testBigqueryClient.js
@@ -0,0 +1,196 @@
+"use strict";
+
+
+const proxyquire = require("proxyquire");
+const { assert } = require("chai");
+import { describe, it } from "mocha";
+const { stub } = require("sinon");
+
+const { BigqueryClient } = require("../analytics_export/bigqueryClient")
+
+describe("BigqueryClient", () => {
+  describe("factory", () => {
+    const mockBigqueryClient = (mockDataset) => (
+      proxyquire(
+        "../analytics_export/bigqueryClient.js",
+        {
+          "@google-cloud/bigquery": {
+            BigQuery: stub().callsFake(() => ({
+              dataset: stub().returns(mockDataset),
+            })),
+          },
+        },
+      )
+    );
+
+    it("should create the dataset if it does not exist", async () => {
+      const mockDataset = {
+        exists: stub().returns([false]),
+        create: stub(),
+      };
+
+      const bigqueryClient = mockBigqueryClient(mockDataset);
+
+      await bigqueryClient.BigqueryClient.createClient(
+        "fake-project",
+        "test_app_store",
+      );
+
+      assert.isTrue(mockDataset.exists.calledOnce);
+      assert.isTrue(mockDataset.create.calledOnce);
+    });
+
+    it("should skip dataset creation if dataset exists", async () => {
+      const mockDataset = {
+        exists: stub().returns([true]),
+        create: stub(),
+      };
+
+      const bigqueryClient = mockBigqueryClient(mockDataset);
+
+      await bigqueryClient.BigqueryClient.createClient(
+        "fake-project",
+        "test_app_store",
+      );
+
+      assert.isTrue(mockDataset.exists.calledOnce);
+      assert.isTrue(mockDataset.create.notCalled);
+    });
+  });
+
+  describe("create table", () => {
+    const tableName = "tabby";
+
+    it("should create table if it does not exist", async () => {
+      const mockTable = {
+        exists: stub().returns([false]),
+      };
+      const mockDataset = {
+        table: stub().returns(mockTable),
+        createTable: stub().returns([tableName]),
+      };
+      const bigqueryClient = new BigqueryClient(mockDataset);
+
+      await bigqueryClient.createTableIfNotExists(tableName, [], "");
+
+      assert.isTrue(mockTable.exists.calledOnce);
+      assert.isTrue(mockDataset.table.calledOnce);
+      assert.isTrue(mockDataset.createTable.calledOnce);
+      assert.isTrue(mockDataset.createTable.calledWith(tableName));
+    });
+
+    it("should skip table creation if table exists", async () => {
+      const mockTable = {
+        exists: stub().returns([true]),
+      };
+      const mockDataset = {
+        table: stub().returns(mockTable),
+        createTable: stub().returns([tableName]),
+      };
+
+      const bigqueryClient = new BigqueryClient(mockDataset);
+
+      await bigqueryClient.createTableIfNotExists(tableName, [], "");
+
+      assert.isTrue(mockTable.exists.calledOnce);
+      assert.isTrue(mockDataset.table.calledOnce);
+      assert.isTrue(mockDataset.createTable.notCalled);
+    });
+  });
+
+  describe("write data", () => {
+    let mockBigqueryClient;
+    let mockTable;
+    let mockDataset;
+    let mockFs;
+
+    beforeEach(() => {
+      mockTable = {
+        exists: stub().returns([true]),
+        load: stub(),
+      };
+      mockDataset = {
+        table: stub().returns(mockTable),
+      };
+
+      mockFs = {
+        writeFileSync: stub(),
+      }
+
+      mockBigqueryClient = proxyquire(
+        "../analytics_export/bigqueryClient.js",
+        {
+          fs: mockFs,
+          tempy: {
+            file: () => "file.csv",
+          },
+        },
+      );
+    });
+
+    it("should give the correct table name based on measure and dimension", async () => {
+      const bqClient = new mockBigqueryClient.BigqueryClient(mockDataset);
+
+      const tableName = await bqClient.writeData(
+        "impressionsTotal",
+        "region",
+        "2020-07-01",
+        [],
+        true,
+      );
+
+      assert.equal(tableName, "impressions_by_region");
+    });
+
+    it("should give the correct table name for null dimensions", async () => {
+      const bqClient = new mockBigqueryClient.BigqueryClient(mockDataset);
+
+      const tableName = await bqClient.writeData(
+        "impressionsTotal",
+        null,
+        "2020-07-01",
+        [],
+        true,
+      );
+
+      assert.equal(tableName, "impressions_total");
+    });
+
+    it("should write the correct data to a temporary file", async () => {
+      const bqClient = new mockBigqueryClient.BigqueryClient(mockDataset);
+
+      const data = [
+        { date: "2020-07-07", app_name: "Firefox", value: 1, region: "a" },
+        { date: "2020-07-07", app_name: "Firefox", value: 2, region: "a" },
+      ]
+
+      const tableName = await bqClient.writeData(
+        "impressionsTotal",
+        "region",
+        "2020-07-01",
+        data,
+        true,
+      );
+
+      const writtenData = "2020-07-07\tFirefox\t1\ta\n2020-07-07\tFirefox\t2\ta";
+      assert.isTrue(mockFs.writeFileSync.calledWith("file.csv", writtenData));
+    });
+
+    it("should write to a partition of the table", async () => {
+      const bqClient = new mockBigqueryClient.BigqueryClient(mockDataset);
+      bqClient.createTableIfNotExists = stub();
+
+      const tableName = await bqClient.writeData(
+        "impressionsTotal",
+        "region",
+        "2020-07-01",
+        [],
+        true,
+      );
+
+      assert.isTrue(mockDataset.table.calledOnce);
+      assert.isTrue(mockDataset.table.calledOnceWithExactly(`${tableName}$20200701`));
+    });
+
+  });
+});
diff --git a/test/testExport.js b/test/testExport.js
index 50b2fc2..507d2d6 100644
--- a/test/testExport.js
+++ b/test/testExport.js
@@ -1,13 +1,10 @@
 "use strict";
 
+import { describe, it } from "mocha";
+
 const analyticsExport = require("../analytics_export/analyticsExport.js");
 
-const chai = require("chai");
-
-chai.should();
-
-describe("Export Functions", function () {
-    it("should pass test", function () {
-        analyticsExport.startExport().should.equal("test");
-    });
+describe("getAllowedDimensionsPerMeasure", () => {
+  it("should fail if given date before data start date", () => {
+  });
 });
diff --git a/yarn.lock b/yarn.lock
index a9335cc..238f421 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -73,6 +73,42 @@
   resolved "https://registry.yarnpkg.com/@google-cloud/promisify/-/promisify-2.0.1.tgz#79f722463a5779197267c6870362b1d7927081f7"
   integrity sha512-82EQzwrNauw1fkbUSr3f+50Bcq7g4h0XvLOk8C5e9ABkXYHei7ZPi9tiMMD7Vh3SfcdH97d1ibJ3KBWp2o1J+w==
 
+"@sinonjs/commons@^1", "@sinonjs/commons@^1.6.0", "@sinonjs/commons@^1.7.0", "@sinonjs/commons@^1.7.2":
+  version "1.8.0"
+  resolved "https://registry.yarnpkg.com/@sinonjs/commons/-/commons-1.8.0.tgz#c8d68821a854c555bba172f3b06959a0039b236d"
+  integrity sha512-wEj54PfsZ5jGSwMX68G8ZXFawcSglQSXqCftWX3ec8MDUzQdHgcKvw97awHbY0efQEL5iKUOAmmVtoYgmrSG4Q==
+  dependencies:
+    type-detect "4.0.8"
+
+"@sinonjs/fake-timers@^6.0.0", "@sinonjs/fake-timers@^6.0.1":
+  version "6.0.1"
+  resolved "https://registry.yarnpkg.com/@sinonjs/fake-timers/-/fake-timers-6.0.1.tgz#293674fccb3262ac782c7aadfdeca86b10c75c40"
+  integrity sha512-MZPUxrmFubI36XS1DI3qmI0YdN1gks62JtFZvxR67ljjSNCeK6U08Zx4msEWOXuofgqUt6zPHSi1H9fbjR/NRA==
+  dependencies:
+    "@sinonjs/commons" "^1.7.0"
+
+"@sinonjs/formatio@^5.0.1":
+  version "5.0.1"
+  resolved "https://registry.yarnpkg.com/@sinonjs/formatio/-/formatio-5.0.1.tgz#f13e713cb3313b1ab965901b01b0828ea6b77089"
+  integrity sha512-KaiQ5pBf1MpS09MuA0kp6KBQt2JUOQycqVG1NZXvzeaXe5LGFqAKueIS0bw4w0P9r7KuBSVdUk5QjXsUdu2CxQ==
+  dependencies:
+    "@sinonjs/commons" "^1"
+    "@sinonjs/samsam" "^5.0.2"
+
+"@sinonjs/samsam@^5.0.2", "@sinonjs/samsam@^5.0.3":
+  version "5.0.3"
+  resolved "https://registry.yarnpkg.com/@sinonjs/samsam/-/samsam-5.0.3.tgz#86f21bdb3d52480faf0892a480c9906aa5a52938"
+  integrity sha512-QucHkc2uMJ0pFGjJUDP3F9dq5dx8QIaqISl9QgwLOh6P9yv877uONPGXh/OH/0zmM3tW1JjuJltAZV2l7zU+uQ==
+  dependencies:
+    "@sinonjs/commons" "^1.6.0"
+    lodash.get "^4.4.2"
+    type-detect "^4.0.8"
+
+"@sinonjs/text-encoding@^0.7.1":
+  version "0.7.1"
+  resolved "https://registry.yarnpkg.com/@sinonjs/text-encoding/-/text-encoding-0.7.1.tgz#8da5c6530915653f3a1f38fd5f101d8c3f8079c5"
+  integrity sha512-+iTbntw2IZPb/anVDbypzfQa+ay64MW0Zo8aJ8gZPWMMK6/OubMVb6lUPMagqjOPnmtauXnFCACVl3O7ogjeqQ==
+
 "@tootallnate/once@1":
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/@tootallnate/once/-/once-1.1.2.tgz#ccb91445360179a04e7fe6aff78c00ffc1eeaf82"
@@ -512,7 +548,7 @@ delayed-stream@~1.0.0:
   resolved "https://registry.yarnpkg.com/delayed-stream/-/delayed-stream-1.0.0.tgz#df3ae199acadfb7d440aaae0b29e2272b24ec619"
   integrity sha1-3zrhmayt+31ECqrgsp4icrJOxhk=
 
-diff@4.0.2:
+diff@4.0.2, diff@^4.0.2:
   version "4.0.2"
   resolved "https://registry.yarnpkg.com/diff/-/diff-4.0.2.tgz#60f3aecb89d5fae520c11aa19efc2bb982aade7d"
   integrity sha512-58lmxKSA4BNyLz+HHMUzlOEpg09FV+ev6ZMe3vJihgdxzgcwZ8VoEEPmALCZG9LmqfVoNMMKpttIYTVG6uDY7A==
@@ -845,6 +881,14 @@ file-entry-cache@^5.0.1:
   dependencies:
     flat-cache "^2.0.1"
 
+fill-keys@^1.0.2:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/fill-keys/-/fill-keys-1.0.2.tgz#9a8fa36f4e8ad634e3bf6b4f3c8882551452eb20"
+  integrity sha1-mo+jb06K1jTjv2tPPIiCVRRS6yA=
+  dependencies:
+    is-object "~1.0.1"
+    merge-descriptors "~1.0.0"
+
 fill-range@^7.0.1:
   version "7.0.1"
   resolved "https://registry.yarnpkg.com/fill-range/-/fill-range-7.0.1.tgz#1919a6a7c75fe38b2c7c77e5198535da9acdda40"
@@ -1204,6 +1248,11 @@ is-number@^7.0.0:
   resolved "https://registry.yarnpkg.com/is-number/-/is-number-7.0.0.tgz#7535345b896734d5f80c4d06c50955527a14f12b"
   integrity sha512-41Cifkg6e8TylSpdtTpeLVMqvSBEVzTttHvERD741+pnZ8ANv0004MRL43QKPDlK9cGvNp6NZWZUBlbGXYxxng==
 
+is-object@~1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/is-object/-/is-object-1.0.1.tgz#8952688c5ec2ffd6b03ecc85e769e02903083470"
+  integrity sha1-iVJojF7C/9awPsyF52ngKQMINHA=
+
 is-regex@^1.1.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/is-regex/-/is-regex-1.1.0.tgz#ece38e389e490df0dc21caea2bd596f987f767ff"
@@ -1243,6 +1292,11 @@ is@^3.3.0:
   resolved "https://registry.yarnpkg.com/is/-/is-3.3.0.tgz#61cff6dd3c4193db94a3d62582072b44e5645d79"
   integrity sha512-nW24QBoPcFGGHJGUwnfpI7Yc5CdqWNdsyHQszVE/z2pKHXzh7FZ5GWhJqSyaQ9wMkQnsTx+kAI8bHlCX4tKdbg==
 
+isarray@0.0.1:
+  version "0.0.1"
+  resolved "https://registry.yarnpkg.com/isarray/-/isarray-0.0.1.tgz#8a18acfca9a8f4177e09abfc6038939b05d1eedf"
+  integrity sha1-ihis/Kmo9Bd+Cav8YDiTmwXR7t8=
+
 isarray@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/isarray/-/isarray-1.0.0.tgz#bb935d48582cba168c06834957a54a3e07124f11"
@@ -1355,6 +1409,11 @@ jsprim@^1.2.2:
     json-schema "0.2.3"
     verror "1.10.0"
 
+just-extend@^4.0.2:
+  version "4.1.0"
+  resolved "https://registry.yarnpkg.com/just-extend/-/just-extend-4.1.0.tgz#7278a4027d889601640ee0ce0e5a00b992467da4"
+  integrity sha512-ApcjaOdVTJ7y4r08xI5wIqpvwS48Q0PBG4DJROcEkH1f8MdAiNFyFxz3xoL0LWAVwjrwPYZdVHHxhRHcx/uGLA==
+
 jwa@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/jwa/-/jwa-2.0.0.tgz#a7e9c3f29dae94027ebcaf49975c9345593410fc"
@@ -1413,6 +1472,11 @@ locate-path@^5.0.0:
   dependencies:
     p-locate "^4.1.0"
 
+lodash.get@^4.4.2:
+  version "4.4.2"
+  resolved "https://registry.yarnpkg.com/lodash.get/-/lodash.get-4.4.2.tgz#2d177f652fa31e939b4438d5341499dfa3825e99"
+  integrity sha1-LRd/ZS+jHpObRDjVNBSZ36OCXpk=
+
 lodash@^4.17.14, lodash@^4.17.15:
   version "4.17.15"
   resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.15.tgz#b447f6670a0455bbfeedd11392eff330ea097548"
@@ -1432,6 +1496,11 @@ lru-cache@^5.0.0:
   dependencies:
     yallist "^3.0.2"
 
+merge-descriptors@~1.0.0:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/merge-descriptors/-/merge-descriptors-1.0.1.tgz#b00aaa556dd8b44568150ec9d1b953f3f90cbb61"
+  integrity sha1-sAqqVW3YtEVoFQ7J0blT8/kMu2E=
+
 mime-db@1.44.0:
   version "1.44.0"
   resolved "https://registry.yarnpkg.com/mime-db/-/mime-db-1.44.0.tgz#fa11c5eb0aca1334b4233cb4d52f10c5a6272f92"
@@ -1499,6 +1568,11 @@ mocha@^8.0.1:
     yargs-parser "13.1.2"
     yargs-unparser "1.6.0"
 
+module-not-found-error@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/module-not-found-error/-/module-not-found-error-1.0.1.tgz#cf8b4ff4f29640674d6cdd02b0e3bc523c2bbdc0"
+  integrity sha1-z4tP9PKWQGdNbN0CsOO8UjwrvcA=
+
 moment@^2.24.0:
   version "2.27.0"
   resolved "https://registry.yarnpkg.com/moment/-/moment-2.27.0.tgz#8bff4e3e26a236220dfe3e36de756b6ebaa0105d"
@@ -1519,6 +1593,17 @@ natural-compare@^1.4.0:
   resolved "https://registry.yarnpkg.com/natural-compare/-/natural-compare-1.4.0.tgz#4abebfeed7541f2c27acfb29bdbbd15c8d5ba4f7"
   integrity sha1-Sr6/7tdUHywnrPspvbvRXI1bpPc=
 
+nise@^4.0.1:
+  version "4.0.4"
+  resolved "https://registry.yarnpkg.com/nise/-/nise-4.0.4.tgz#d73dea3e5731e6561992b8f570be9e363c4512dd"
+  integrity sha512-bTTRUNlemx6deJa+ZyoCUTRvH3liK5+N6VQZ4NIw90AgDXY6iPnsqplNFf6STcj+ePk0H/xqxnP75Lr0J0Fq3A==
+  dependencies:
+    "@sinonjs/commons" "^1.7.0"
+    "@sinonjs/fake-timers" "^6.0.0"
+    "@sinonjs/text-encoding" "^0.7.1"
+    just-extend "^4.0.2"
+    path-to-regexp "^1.7.0"
+
 node-fetch@^2.2.0, node-fetch@^2.3.0, node-fetch@^2.6.0:
   version "2.6.0"
   resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-2.6.0.tgz#e633456386d4aa55863f676a7ab0daa8fdecb0fd"
@@ -1710,6 +1795,13 @@ path-parse@^1.0.6:
   resolved "https://registry.yarnpkg.com/path-parse/-/path-parse-1.0.6.tgz#d62dbb5679405d72c4737ec58600e9ddcf06d24c"
   integrity sha512-GSmOT2EbHrINBf9SR7CDELwlJ8AENk3Qn7OikK4nFYAu3Ote2+JYNVvkpAEQm3/TLNEJFD/xZJjzyxg3KBWOzw==
 
+path-to-regexp@^1.7.0:
+  version "1.8.0"
+  resolved "https://registry.yarnpkg.com/path-to-regexp/-/path-to-regexp-1.8.0.tgz#887b3ba9d84393e87a0a0b9f4cb756198b53548a"
+  integrity sha512-n43JRhlUKUAlibEJhPeir1ncUID16QnEjNpwzNdO3Lm4ywrBpBZ5oLD0I6br9evr1Y9JTqwRtAh7JLoOzAQdVA==
+  dependencies:
+    isarray "0.0.1"
+
 path-type@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/path-type/-/path-type-2.0.0.tgz#f012ccb8415b7096fc2daa1054c3d72389594c73"
@@ -1770,6 +1862,15 @@ promise.allsettled@1.0.2:
     function-bind "^1.1.1"
     iterate-value "^1.0.0"
 
+proxyquire@^2.1.3:
+  version "2.1.3"
+  resolved "https://registry.yarnpkg.com/proxyquire/-/proxyquire-2.1.3.tgz#2049a7eefa10a9a953346a18e54aab2b4268df39"
+  integrity sha512-BQWfCqYM+QINd+yawJz23tbBM40VIGXOdDw3X344KcclI/gtBbdWF6SlQ4nK/bYhF9d27KYug9WzljHC6B9Ysg==
+  dependencies:
+    fill-keys "^1.0.2"
+    module-not-found-error "^1.0.1"
+    resolve "^1.11.1"
+
 psl@^1.1.28:
   version "1.8.0"
   resolved "https://registry.yarnpkg.com/psl/-/psl-1.8.0.tgz#9326f8bcfb013adcc005fdff056acce020e51c24"
@@ -1880,7 +1981,7 @@ resolve-from@^4.0.0:
   resolved "https://registry.yarnpkg.com/resolve-from/-/resolve-from-4.0.0.tgz#4abcd852ad32dd7baabfe9b40e00a36db5f392e6"
   integrity sha512-pb/MYmXstAkysRFx8piNI1tGFNQIFA3vkE3Gq4EuA1dF6gHp/+vgZqsCGJapvy8N3Q+4o7FwvquPJcnZ7RYy4g==
 
-resolve@^1.10.0, resolve@^1.13.1, resolve@^1.17.0:
+resolve@^1.10.0, resolve@^1.11.1, resolve@^1.13.1, resolve@^1.17.0:
   version "1.17.0"
   resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.17.0.tgz#b25941b54968231cc2d1bb76a79cb7f2c0bf8444"
   integrity sha512-ic+7JYiV8Vi2yzQGFWOkiZD5Z9z7O2Zhm9XMaTxdJExKasieFCr+yXZ/WmXsckHiKl12ar0y6XiXDx3m4RHn1w==
@@ -1944,6 +2045,19 @@ shebang-regex@^3.0.0:
   resolved "https://registry.yarnpkg.com/shebang-regex/-/shebang-regex-3.0.0.tgz#ae16f1644d873ecad843b0307b143362d4c42172"
   integrity sha512-7++dFhtcx3353uBaq8DDR4NuxBetBzC7ZQOhmTQInHEd6bSrXdiEyzCvG07Z44UYdLShWUyXt5M/yhz8ekcb1A==
 
+sinon@^9.0.2:
+  version "9.0.2"
+  resolved "https://registry.yarnpkg.com/sinon/-/sinon-9.0.2.tgz#b9017e24633f4b1c98dfb6e784a5f0509f5fd85d"
+  integrity sha512-0uF8Q/QHkizNUmbK3LRFqx5cpTttEVXudywY9Uwzy8bTfZUhljZ7ARzSxnRHWYWtVTeh4Cw+tTb3iU21FQVO9A==
+  dependencies:
+    "@sinonjs/commons" "^1.7.2"
+    "@sinonjs/fake-timers" "^6.0.1"
+    "@sinonjs/formatio" "^5.0.1"
+    "@sinonjs/samsam" "^5.0.3"
+    diff "^4.0.2"
+    nise "^4.0.1"
+    supports-color "^7.1.0"
+
 slice-ansi@^2.1.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/slice-ansi/-/slice-ansi-2.1.0.tgz#cacd7693461a637a5788d92a7dd4fba068e81636"
@@ -2213,7 +2327,7 @@ type-check@^0.4.0, type-check@~0.4.0:
   dependencies:
     prelude-ls "^1.2.1"
 
-type-detect@^4.0.0, type-detect@^4.0.5:
+type-detect@4.0.8, type-detect@^4.0.0, type-detect@^4.0.5, type-detect@^4.0.8:
   version "4.0.8"
   resolved "https://registry.yarnpkg.com/type-detect/-/type-detect-4.0.8.tgz#7646fb5f18871cfbb7749e69bd39a6388eb7450c"
   integrity sha512-0fr/mIH1dlO+x7TlcMy+bIDqKPsw/70tVyeHW787goQjhmqaZe10uwLujubK9q9Lg6Fiho1KUKDYz0Z7k7g5/g==