def test_weighted_dbscan():
    # ensure sample_weight is validated
    assert_raises(ValueError, dbscan, [[0], [1]], sample_weight=[2])
    assert_raises(ValueError, dbscan, [[0], [1]], sample_weight=[2, 3, 4])

    # ensure sample_weight has an effect
    assert_array_equal([], dbscan([[0], [1]], sample_weight=None, min_samples=6)[0])
    assert_array_equal([], dbscan([[0], [1]], sample_weight=[5, 5], min_samples=6)[0])
    assert_array_equal([0], dbscan([[0], [1]], sample_weight=[6, 5], min_samples=6)[0])
    assert_array_equal([0, 1], dbscan([[0], [1]], sample_weight=[6, 6], min_samples=6)[0])

    # points within eps of each other:
    assert_array_equal([0, 1], dbscan([[0], [1]], eps=1.5, sample_weight=[5, 1], min_samples=6)[0])
    # and effect of non-positive and non-integer sample_weight:
    assert_array_equal([], dbscan([[0], [1]], sample_weight=[5, 0], eps=1.5, min_samples=6)[0])
    assert_array_equal([0, 1], dbscan([[0], [1]], sample_weight=[5.9, 0.1], eps=1.5, min_samples=6)[0])
    assert_array_equal([0, 1], dbscan([[0], [1]], sample_weight=[6, 0], eps=1.5, min_samples=6)[0])
    assert_array_equal([], dbscan([[0], [1]], sample_weight=[6, -1], eps=1.5, min_samples=6)[0])

    # for non-negative sample_weight, cores should be identical to repetition
    rng = np.random.RandomState(42)
    sample_weight = rng.randint(0, 5, X.shape[0])
    core1, label1 = dbscan(X, sample_weight=sample_weight)
    assert_equal(len(label1), len(X))

    X_repeated = np.repeat(X, sample_weight, axis=0)
    core_repeated, label_repeated = dbscan(X_repeated)
    core_repeated_mask = np.zeros(X_repeated.shape[0], dtype=bool)
    core_repeated_mask[core_repeated] = True
    core_mask = np.zeros(X.shape[0], dtype=bool)
    core_mask[core1] = True
    assert_array_equal(np.repeat(core_mask, sample_weight), core_repeated_mask)

    # sample_weight should work with precomputed distance matrix
    D = pairwise_distances(X)
    core3, label3 = dbscan(D, sample_weight=sample_weight, metric="precomputed")
    assert_array_equal(core1, core3)
    assert_array_equal(label1, label3)

    # sample_weight should work with estimator
    est = DBSCAN().fit(X, sample_weight=sample_weight)
    core4 = est.core_sample_indices_
    label4 = est.labels_
    assert_array_equal(core1, core4)
    assert_array_equal(label1, label4)

    est = DBSCAN()
    label5 = est.fit_predict(X, sample_weight=sample_weight)
    core5 = est.core_sample_indices_
    assert_array_equal(core1, core5)
    assert_array_equal(label1, label5)
    assert_array_equal(label1, est.labels_)

def test_dbscan_balltree():
    # Tests the DBSCAN algorithm with balltree for neighbor calculation.
    eps = 0.8
    min_samples = 10

    D = pairwise_distances(X)
    core_samples, labels = dbscan(D, metric="precomputed", eps=eps, min_samples=min_samples)

    # number of clusters, ignoring noise if present
    n_clusters_1 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_1, n_clusters)

    db = DBSCAN(p=2.0, eps=eps, min_samples=min_samples, algorithm="ball_tree")
    labels = db.fit(X).labels_

    n_clusters_2 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_2, n_clusters)

    db = DBSCAN(p=2.0, eps=eps, min_samples=min_samples, algorithm="kd_tree")
    labels = db.fit(X).labels_

    n_clusters_3 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_3, n_clusters)

    db = DBSCAN(p=1.0, eps=eps, min_samples=min_samples, algorithm="ball_tree")
    labels = db.fit(X).labels_

    n_clusters_4 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_4, n_clusters)

    db = DBSCAN(leaf_size=20, eps=eps, min_samples=min_samples, algorithm="ball_tree")
    labels = db.fit(X).labels_

    n_clusters_5 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_5, n_clusters)

def test_dbscan_feature():
    # Tests the DBSCAN algorithm with a feature vector array.
    # Parameters chosen specifically for this task.
    # Different eps to other test, because distance is not normalised.
    eps = 0.8
    min_samples = 10
    metric = "euclidean"
    # Compute DBSCAN
    # parameters chosen for task
    core_samples, labels = dbscan(X, metric=metric, eps=eps, min_samples=min_samples)

    # number of clusters, ignoring noise if present
    n_clusters_1 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_1, n_clusters)

    db = DBSCAN(metric=metric, eps=eps, min_samples=min_samples)
    labels = db.fit(X).labels_

    n_clusters_2 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_2, n_clusters)

def test_dbscan_similarity():
    # Tests the DBSCAN algorithm with a similarity array.
    # Parameters chosen specifically for this task.
    eps = 0.15
    min_samples = 10
    # Compute similarities
    D = distance.squareform(distance.pdist(X))
    D /= np.max(D)
    # Compute DBSCAN
    core_samples, labels = dbscan(D, metric="precomputed", eps=eps, min_samples=min_samples)
    # number of clusters, ignoring noise if present
    n_clusters_1 = len(set(labels)) - (1 if -1 in labels else 0)

    assert_equal(n_clusters_1, n_clusters)

    db = DBSCAN(metric="precomputed", eps=eps, min_samples=min_samples)
    labels = db.fit(D).labels_

    n_clusters_2 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_2, n_clusters)

def test_dbscan_callable():
    # Tests the DBSCAN algorithm with a callable metric.
    # Parameters chosen specifically for this task.
    # Different eps to other test, because distance is not normalised.
    eps = 0.8
    min_samples = 10
    # metric is the function reference, not the string key.
    metric = distance.euclidean
    # Compute DBSCAN
    # parameters chosen for task
    core_samples, labels = dbscan(X, metric=metric, eps=eps, min_samples=min_samples, algorithm="ball_tree")

    # number of clusters, ignoring noise if present
    n_clusters_1 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_1, n_clusters)

    db = DBSCAN(metric=metric, eps=eps, min_samples=min_samples, algorithm="ball_tree")
    labels = db.fit(X).labels_

    n_clusters_2 = len(set(labels)) - int(-1 in labels)
    assert_equal(n_clusters_2, n_clusters)